Control device of internal combustion engine

ABSTRACT

A control device of an internal combustion engine calculates on the basis of the air-fuel ratio difference a correction for the estimated fuel supply amount correction for correcting the estimated fuel supply amount to make the estimated and detected air-fuel ratios correspond to each other and calculates correction values for the fuel supply difference compensation and the air amount detection difference compensation by dividing the correction value for the estimated fuel supply amount correction, using the fuel supply and air amount detection difference proportions, and performing the air-fuel ratio control, using the corrected estimated fuel supply and detected air amounts. The correction value for the estimated fuel supply amount correction is divided to the correction values for the fuel supply difference compensation and the air amount detection difference compensation such that a value equivalent to the air-fuel ratio difference becomes equal to the air-fuel ratio difference, using these correction values.

TECHNICAL FIELD

This invention relates to a control device of an internal combustionengine.

BACKGROUND ART

A control device of an internal combustion engine is described in thePatent Document 1.

The engine of the Document 1 comprises fuel injectors, an air flow meterand an air-fuel ratio sensor.

The injector injects a fuel when a command corresponding to a targetfuel injection amount (hereinafter, this command will be referred toas—fuel injection command—) is given to the injector. In the case thatthe injector can inject the fuel of the amount corresponding to thecommand exactly, that is, the injector has no error, the fuel of theamount corresponding to the target amount is injected from the injector.

The air flow meter outputs an output value corresponding to an amount ofan air flowing therethrough (hereinafter, this amount will be referredto as—fresh air amount—).

The control device calculates the fresh air amount on the basis of theoutput value of the air flow meter. That is, the air flow meter detectsthe fresh air amount. In the case that the air flow meter can output anoutput value exactly corresponding to the actual fresh air amount, thatis, the air flow meter has no error, the fresh air amount is exactlycalculated on the basis of the output value of the air flow meter. Thatis, the air flow meter exactly detects the fresh air amount.

The air-fuel ratio sensor outputs an output value corresponding to anair-fuel ratio of a mixture gas formed in the combustion chamber of theengine (i.e. a gas of a mixed air and fuel and hereinafter, this gaswill be referred simply to as—mixture gas—).

The control device calculates the air-fuel ratio of the mixture gas onthe basis of the output value of the air-fuel ratio sensor. That is, theair-fuel ratio sensor detects the air-fuel ratio of the mixture gas.

In the case that the injector and the air flow meter have no error, theair-fuel ratio of the mixture gas calculated (hereinafter, this ratiowill be referred to as—estimated air-fuel ratio—) from the fuelinjection amount corresponding to the fuel injection command and thefresh air amount detected by the air flow meter (hereinafter, thisamount will be referred to as—detected fresh air amount) corresponds tothe air-fuel ratio of the mixture gas detected by the air-fuel ratiosensor (hereinafter, this ratio will be referred to as—detected air-fuelratio—).

In other words, in the case that the injector or the air flow meter hasan error, the estimated air-fuel ratio may become corresponding to thedetected air-fuel ratio incidentally, however, in many cases, theestimated air-fuel ratio does not become corresponding to the detectedair-fuel ratio.

Therefore, in the case that the estimated air-fuel ratio does notcorrespond to the detected air-fuel ratio, it can be judged that theinjector or the air flow meter has an error.

There is a control using the fuel injection amount understood from thefuel injection command (hereinafter, this amount will be referred toas—commanded fuel injection amount—) or detected fresh air amount as anengine control.

If the injector has no error, the desired object of this control can beaccomplished even when this control is performed using the commandedfuel injection amount itself or if the air flow meter has no error, thedesired object of this control can be accomplished even when thiscontrol is performed using the detected fresh air amount itself.

However, in the case that the injector has an error, when the control isperformed using the commanded fuel injection amount itself, the desiredobject of this control is not accomplished and in the case that the airflow meter has an error, when the control is performed using thedetected fresh air amount itself, the desired object of this control isnot accomplished.

Therefore, in order to accomplish the desired object of each control,when the injector has an error, the control should be performed usingthe commanded fuel injection amount appropriately corrected and when theair flow meter has an error, the control should be performed using thedetected fresh air appropriately corrected.

That is, when the estimated air-fuel ratio does not correspond to thedetected air-fuel ratio, it can be judged that the injector or the airflow meter has an error and therefore, the commanded fuel injectionamount or the detected fresh air amount should be corrected.

In the device of the Document 1, when the estimated air-fuel ratio doesnot correspond to the detected air-fuel ratio, the commanded fuelinjection amount and the detected fresh air amount are corrected asfollows.

In the device of the Document 1, a ratio of the estimated air-fuel ratiorelative to the detected air-fuel ratio (i.e. the estimated air-fuelratio/detected air-fuel ratio and hereinafter, this will be referred toas—air-fuel-ratio —) is calculated during the engine operation.

Then, when the estimated air-fuel ratio corresponds to the detectedair-fuel ratio, the air-fuel-ratio is “1” and therefore, a value iscalculated by subtracting “1” from the air-fuel-ratio calculated in thecase that the estimated air-fuel ratio does not correspond to thedetected air-fuel ratio (=the ratio of the air-fuel ratio−1 andhereinafter, this value will be referred to as—air-fuel ratiodifference—).

On the other hand, influences of the fuel injection difference and thefresh air amount detection difference maximally given to the air-fuelratio difference are obtained by an experience, etc. and a rate of theair-fuel ratio difference due to the fuel injection difference in theair-fuel ratio (this rate is smaller than “1” and hereinafter, will bereferred to as—fuel injection difference proportion) and a rate of theair-fuel ratio difference due to the fresh air amount detectiondifference (this rate is smaller than “1” and will be referred toas—fresh air amount detection difference proportion—) are previouslyobtained.

The sum of the fuel injection and fresh air amount detection differenceproportions (=the fuel injection difference proportion+the fresh airamount detection difference proportion) is “1”.

In the device of the Document 1, the fuel injection difference rate iscalculated by multiplying the air-fuel ratio difference calculatedduring the engine operation by the fuel injection difference proportion(=the air-fuel ratio difference×the fuel injection differenceproportion) and the fresh air amount detection difference rate iscalculated by multiplying the air-fuel ratio difference calculatedduring the engine operation by the fresh air amount detection differenceproportion (=the air-fuel ratio difference×the fresh air amountdetection difference proportion).

When the air-fuel-ratio is larger than “1”, the estimated air-fuel ratiois larger than the detected air-fuel ratio, that is, the estimatedair-fuel ratio is leaner than the detected air-fuel ratio and therefore,it can be understood that the amount of the fuel injected actually fromthe injector (hereinafter, this amount will be referred to as—actualfuel injection amount—) is smaller than the commanded fuel injectionamount and the actual fresh air amount is larger than the detected freshair amount.

In this case, it is necessary to correct the fuel injection commandcorresponding to the target fuel injection amount so as to increase thecommand in order to make the injector inject the fuel of the amountcorresponding to the target amount and it is necessary to correct thedetected fresh air amount so as to increase the amount in order todetect the actual fresh air amount on the basis of the output value ofthe air flow meter.

In the device of the Document 1, the fuel injection command is correctedby multiplying this command by a value obtained by adding the fuelinjection difference rate to “1” (=the fuel injection command×(1+thefuel injection difference rate)) and the detected fresh air amount iscorrected by multiplying this amount by a value obtained by adding thefresh air amount detection difference rate to “1” (=the detected freshair amount×(1+the fresh air amount detection difference rate)).

When the air-fuel-ratio is smaller than “1”, the estimated air-fuelratio is smaller than the detected air-fuel ratio, that is, theestimated air-fuel ratio is richer than the detected air-fuel ratio andtherefore, it can be understood that the actual fuel injection amount islarger than the commanded fuel injection amount and the actual fresh airamount is smaller than the detected fresh air amount.

In this case, it is necessary to correct the fuel injection commandcorresponding to the target fuel injection amount so as to decrease thiscommand in order to make the injector inject the fuel of the amountcorresponding to the target fuel injection amount and it is necessary tocorrect the detected fresh air amount so as to decrease this amount inorder to detect the actual fresh air amount on the basis of the outputvalue of the air flow meter.

In the device of the Document 1, the fuel injection command is correctedby multiplying this command by a value obtained by subtracting the fuelinjection difference rate from “1” (=the fuel injection command×(1−thefuel injection difference rate)) and the detected fresh air amount iscorrected by multiplying this amount by a value obtained by the freshair amount detection difference rate from “1” (=the detected fresh airamount×(1−the fresh air amount detection rate)).

PRIOR ART DOCUMENTS Patent Document

-   [PATENT DOCUMENT 1] Unexamined Japanese Patent Publication No.    2007-262946

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In order to make the estimated air-fuel ratio correspond to the detectedair-fuel ratio for a relatively short time, when a ratio of a valueobtained by adding the fresh air amount detection difference rate,calculated in the case that the air-fuel-ratio is larger than “1”, to“1” (=1+the fresh air amount detection difference rate) relative to avalue obtained by adding the fuel injection difference rate, calculatedin the case that the air-fuel-ratio is larger than “1”, to “1” (=1+thefuel injection difference rate) (=(1+the fresh air amount detectiondifference rate)/(1+the fuel injection difference rate), andhereinafter, this ratio will be referred to as—difference ratio—)corresponds to the air-fuel-ratio, the fact has been realized by thestudy of the inventor of this application that the air-fuel ratiodifference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the fresh airamount detection difference, respectively.

Similarly, in order to make the estimated air-fuel ratio correspond tothe detected air-fuel ratio for a relatively short time, when a ratio ofa value obtained by subtracting the fresh air amount detectiondifference rate, calculated in the case that the air-fuel-ratio issmaller than “1”, from “1” (=1−the fresh air amount detection differencerate) relative to a value obtained by subtracting the fuel injectiondifference rate, calculated in the case that the air-fuel-ratio issmaller than “1”, from “1” (=1−the fuel injection difference rate)(=(1−the fresh air detection difference rate)/(1−the fuel injectiondifference rate) and hereinafter, this ratio will be referred toas—difference ratio—) corresponds to the air-fuel-ratio ratio, the facthas been realized by the study of the inventor of this application thatthe air-fuel ratio difference is distributed appropriately to theair-fuel ratio differences due to the fuel injection difference and thefresh air amount detection difference, respectively.

That is, in general, in the case of setting a correction value forcorrecting a parameter/parameters relating to the fuel injection amountto compensate the fuel injection difference and a correction value forcorrecting a parameter/parameters relating to the fresh air amount tocompensate the fresh air amount detection difference on the basis of oneair-fuel ratio obtained by the estimated and detected air-fuel ratios,when a value equivalent to the air-fuel ratio difference calculated fromthese correction values corresponds to the air-fuel ratio difference, ithas been realized by the inventor of this application that the air-fuelratio difference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the fresh airamount detection differences, respectively.

In the device of the Document 1, the difference ratios under thecondition where the air-fuel-ratio is larger than “1” and is smallerthan “1” do not correspond to the air-fuel-ratio.

Therefore, in the device of the Document 1, it can be understood thatthe air-fuel ratio difference is not distributed appropriately to theair-fuel ratio differences due to the fuel injection difference and thefresh air amount detection difference.

Because of this, even if the fuel injection command and the detectedfresh air amount are corrected by the device of the Document 1, it takesrelatively long time for making the estimated air-fuel ratio tocorrespond to the detected air-fuel ratio.

The appropriate distribution of the air-fuel ratio difference toair-fuel ratio differences due to the fuel injection difference and thefresh air amount detection difference is useful for making the estimatedair-fuel ratio correspond to the detected air-fuel ratio for arelatively short time.

The object of the invention is to distribute the air-fuel ratiodifference appropriately to the air-fuel ratio differences due to thefuel injection difference and the fresh air amount detection difference.

Means for Solving the Problems

The invention of this application relates to a control device of aninternal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying thefuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating an amount of the fuel supplied from the fuel supplymeans to the combustion chamber on the basis of the command given fromthe fuel supply command means to the fuel supply means;

means for controlling an amount of an air supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means;

means for detecting the amount of the air supplied to the combustionchamber;

means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of a fuel amount estimated by the fuelsupply amount estimation means and an air amount detected by the airamount detection means;

means for detecting the air-fuel ratio of the mixture gas formed in thecombustion chamber; and

means for performing a control for making the air-fuel ratio of themixture gas estimated by the air-fuel ratio estimation means and theair-fuel ratio of the mixture gas detected by the air-fuel ratiodetection means correspond to each other, using the estimated fuelsupply amount and the detected air amount or the air supply command.

The device of the invention calculates on the basis of a difference ofthe estimated air-fuel ratio relative to the detected air-fuel ratio, acorrection value for correcting the fuel supply amount estimated by thefuel supply amount estimation means to make the estimated and detectedair-fuel ratios correspond to each other when the estimated and detectedair-fuel ratios do not correspond to each other,

acquires as a fuel supply difference proportion, a rate of the air-fuelratio difference due to the fuel supply difference of the fuel supplymeans occupying the air-fuel ratio difference and as an air amountdetection difference proportion, a rate of the air-fuel ratio differencedue to the air amount detection difference of the air amount detectionmeans occupying the air-fuel ratio difference,

calculates a correction value for correcting the estimated fuel supplyamount and a correction value for correcting the detected air amount orthe air supply command by dividing the correction value for theestimated fuel supply amount compensation, using the fuel supply and airamount detection difference proportions, and

performs the air-fuel ratio control, using the estimated fuel supplyamount corrected by the correction value for the fuel supply differencecompensation and the detected air amount or the air supply commandcorrected by the correction value for the air amount detectiondifference compensation.

In order to accomplish the above-mentioned object, in the device of theinvention, the correction value for the estimated fuel supply amountcorrection is divided to the correction value for the fuel supplydifference compensation and the correction value for the air amountdetection difference compensation such that a value equivalent to theair-fuel ratio difference calculated using the correction values for thefuel supply difference compensation and the air amount detectiondifference compensation corresponds to the air-fuel ratio difference.

According to the invention, the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the difference of the estimatedair-fuel ratio relative to the detected air-fuel ratio.

When the air-fuel ratio difference equivalent value, which is a valueequivalent to the air-fuel ratio difference, is calculated from thesecorrection values, the correction values for the fuel supply differencecompensation and the air amount detection difference compensation areset such that the air-fuel ratio difference equivalent value correspondsto the air-fuel ratio difference (i.e. the value as the base of thesetting of the correction values for the fuel supply differencecompensation and the air amount detection difference compensation).

When the air-fuel ratio difference equivalent value is equal to theair-fuel ratio difference, the air-fuel ratio control using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation is one under the conditionwhere the air-fuel ratio difference is distributed appropriately to theair-fuel ratio differences due to the fuel injection difference and theair amount detection difference, respectively.

Therefore, according to the invention, an effect obtained by theair-fuel ratio control becomes high.

The fuel supply means of the invention is not limited to a particularmeans and may be a fuel injector.

The air supply amount control means of the invention is not limited to aparticular means and may be a throttle valve.

When the invention is applied to the engine comprising an exhaust gasrecirculation device for recirculating to an intake passage, an exhaustgas discharged from the combustion chamber to an exhaust passage, whichdevice having a valve for controlling an amount of the exhaust gasrecirculated to the intake passage, the air supply amount control meansof the invention may be the recirculated exhaust gas amount controlvalve.

When the invention is applied to the engine comprising a superchargerhaving an exhaust turbine arranged in the exhaust passage and acompressor arranged in the intake passage, which supercharger has vanesof the exhaust turbine for controlling a compression force to the air bythe compressor, the air supply amount control means of the invention maybe the vanes.

The air amount detection means of the invention is not limited to aparticular means and may be an air flow meter arranged in the intakepassage.

The air-fuel ratio detection means of the invention is not limited to aparticular means and may be an oxygen concentration sensor.

The air-fuel ratio difference of the invention may be any valueindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference equivalent valuecalculated by subtracting 1 from the ratio of the estimated air-fuelratio relative to the detected air-fuel ratio.

In this case, the correction value for the estimated fuel supply amountcorrection is calculated as a value for making the difference equivalentvalue zero.

The method for obtaining the fuel supply difference proportion and theair amount detection difference proportion are not limited to aparticular method and the following method may be preferred.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has a fuel supply difference and the air amountdetection means has no air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation and the detected airamount or the air supply command corrected by the correction value forthe air amount detection difference compensation under the conditionwhere the fuel supply means has a fuel supply difference and the airamount detection means has no air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference and the air amountdetection means has an air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation and the detected airamount or the air supply command corrected by the correction value forthe air amount detection difference compensation under the conditionwhere the fuel supply means has no fuel supply difference and the airamount detection means has an air amount detection difference.

Then, it is preferred that the fuel supply and air amount detectiondifference proportions are obtained on the basis of the four acquiredparticular component amounts.

According to the invention, when the fuel supply means has a fuel supplydifference (for example, a drawing tolerance of the manufacturing of thefuel supply means) and the air amount detection means has an air amountdetection difference (for example, a drawing tolerance of themanufacturing of the air amount detection means), the fuel supply andair amount detection difference proportions depending on the errors ofthe fuel supply means and the air amount detection means, are used forthe air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering the fuelsupply difference of the fuel supply means and the air amount detectiondifference of the air amount detection means and therefore, the effectobtained from the air-fuel ratio control becomes high.

For example, it is preferred that the fuel supply and air amountdetection difference proportions are obtained as follows.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has a fuel supply difference, the air amount detectionmeans has no air amount detection difference and the air-fuel ratiodetection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation and the detected airamount or the air supply command corrected by the correction value forthe air amount detection difference compensation under the conditionwhere the fuel supply means has a fuel supply difference, the air amountdetection means has no air amount detection difference and the air-fuelratio detection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference, the air amountdetection means has an air amount detection difference and the air-fuelratio detection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation and the detected airamount or the air supply command corrected by the correction value forthe air amount detection difference compensation under the conditionwhere the fuel supply means has no fuel supply difference, the airamount detection means has an air amount detection difference and theair-fuel ratio detection means has no air-fuel ratio detectiondifference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference, the air amountdetection means has no air amount detection means difference and theair-fuel ratio detection means has an air-fuel ratio detectiondifference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount not corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference, the air amountdetection means has no air amount detection difference, and the air-fuelratio detection means has an air-fuel ratio detection difference.

Then, it is preferred that the fuel supply and air amount detectiondifference proportions are obtained on the basis of the acquired sixparticular component amounts.

According to this invention, when the fuel supply means has a fuelsupply difference (for example, a drawing tolerance of the manufacturingof the fuel supply means), the air amount detection means an air amountdetection difference (for example, a drawing tolerance of themanufacturing of the air amount detection means) and the air-fuel ratiodetection means has an air-fuel ratio detection difference (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply and air amount detection difference proportionsdepending on the fuel supply difference of the fuel supply means, theair amount detection difference of the air amount detection means andthe air-fuel ratio detection difference of the air-fuel ratio detectionmeans, are used for the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering thesethree differences and therefore, the effect obtained from the air-fuelratio control becomes high.

Another invention of this application relates to a control device of aninternal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying afuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating an amount of the fuel supplied to the combustionchamber from the fuel supply means on the basis of the command givenfrom the fuel supply command means to the fuel supply means;

means for controlling an amount of an air supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means;

means for detecting the amount of the air supplied to the combustionchamber;

means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of the fuel amount estimated by the fuelsupply amount estimation means and the air amount detected by the airamount detection means;

means for detecting the air-fuel ratio of the mixture gas formed in thecombustion chamber; and

means for performing an air-fuel ratio control for making the air-fuelratio of the mixture gas estimated by the air-fuel ratio estimationmeans and the air-fuel ratio of the mixture gas detected by the air-fuelratio detection means correspond to each other, using the fuel supplycommand and the detected air amount or the air supply command.

The device of this invention calculates on the basis of a difference ofthe estimated air-fuel ratio relative to the detected air-fuel ratio, acorrection value for correcting the command given to the fuel supplymeans to make the estimated and detected air-fuel ratios correspond toeach other when the estimated and detected air-fuel ratios do notcorrespond to each other,

acquires as a fuel supply difference proportion, a rate of the air-fuelratio difference due to the fuel supply difference of the fuel supplymeans occupying the air-fuel ratio difference and acquires as an airamount detection difference proportion, a rate of the air-fuel ratiodifference due to the air amount detection difference of the air amountdetection means occupying the air-fuel ratio difference,

calculates correction values for correcting the fuel supply command andthe detected air amount or the air supply command by dividing thecorrection value for the fuel supply command correction, using the fuelsupply and air amount detection difference proportions,

performs the air-fuel ratio control, using the fuel supply commandcorrected by the correction value for the fuel supply differencecompensation and the detected air amount or the air supply commandcorrected by the correction value for the air amount detectiondifference compensation.

In order to accomplish the above-mentioned object, in the device of thisinvention, the correction value for the fuel supply command correctionis divided to the correction values for the fuel supply differencecompensation and the air amount detection difference compensation suchthat the air-fuel ratio difference equivalent value, which is a valueequivalent to the air-fuel ratio difference calculated using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation, corresponds to theair-fuel ratio difference.

According to this invention, the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the difference of the estimatedair-fuel ratio relative to the detected air amount.

The correction values for the fuel supply difference compensation andthe air amount detection difference compensation are set such that theair-fuel ratio difference equivalent value calculated from thesecorrection values as a value equivalent to the air-fuel ratiodifference, corresponds to the air-fuel ratio difference (i.e. a valueas the base of the setting of the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation).

When the air-fuel difference equivalent value is equal to the air-fuelratio difference, the air-fuel ratio control using these correctionvalues is a control under the condition where the air-fuel ratiodifference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the air amountdetection difference.

Therefore, according to this invention, the effect obtained from theair-fuel ratio becomes high.

The air-fuel ratio difference of this invention may be any valueindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference equivalent valuecalculated by subtracting 1 from the ratio of the estimated air-fuelratio relative to the detected air-fuel ratio.

In this case, the correction value for the fuel supply commandcorrection is calculated as a value for making the difference equivalentvalue zero.

The method for obtaining the fuel supply and air amount detectiondifference proportions is not limited to a particular one and thefollowing method may be preferred.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has a fuel supply difference and the air amount detectionmeans has no air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the fuel supply command not corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has a fuel supply difference and the air amountdetection means has no air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has no fuel supply difference and the air amount detectionmeans has an air amount detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the fuel supply command not corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference and the air amountdetection means has an air amount detection difference.

Then, it is preferred that the fuel supply and air amount detectiondifference proportions are obtained on the basis of the acquired fourparticular component amounts.

According to this invention, when the fuel supply means has a fuelsupply difference (for example, a drawing tolerance of the manufacturingof the fuel supply means) and the air amount detection means has an airamount detection difference (for example, a drawing tolerance of themanufacturing of the air amount detection means), the fuel supply andair amount detection difference proportions depending on the fuel supplydifference of the fuel supply means and the air amount detectiondifference of the air amount detection means, are used for the air-fuelratio control.

Therefore, the air-fuel ratio control is performed considering the fuelsupply difference of the fuel supply means and the air amount detectiondifference of the air amount detection means and therefore, an effectobtained by the air-fuel ratio control becomes high.

For example, it is preferred that the fuel supply and air amountdetection difference proportions are obtained as follows.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has a fuel supply difference, the air amount detectionmeans has no air amount detection difference and the air-fuel ratiodetection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the fuel supply command not corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has a fuel supply difference, the air amount detectionmeans has no air amount detection difference and the air-fuel ratiodetection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has no fuel supply difference, the air amount detectionmeans has an air amount detection difference and the air-fuel ratiodetection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the fuel supply command not corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no fuel supply difference, the air amountdetection means has an air amount detection difference and the air fuelratio detection means has no air-fuel ratio detection difference.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air amount detection means have no error and theair-fuel ratio detection means has an error.

Further, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent amount when the air-fuel ratio control is performed using thefuel supply command not corrected by the correction value for the fuelsupply difference compensation and the detected air amount or the airsupply command corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air amount detection means have no error and theair-fuel ratio detection means has an error.

Then, it is preferred that the fuel supply and air amount detectiondifference proportions are obtained on the basis of the acquired sixparticular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means), the air amount detection means has an error (for example,a drawing tolerance of the manufacturing of the air amount detectionmeans) and the air-fuel ratio detection means has an error (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply and air amount detection difference proportionsdepending on the errors of the fuel supply means, the air amountdetection means and the air-fuel ratio detection means, are used for theair-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means, the air amount detection means and theair-fuel ratio detection means and therefore, the effect obtained fromthe air-fuel ratio becomes high.

Further another invention of this application relates to a controldevice of an internal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying thefuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating the amount of the fuel supplied from the fuelsupply means to the combustion chamber on the basis of the command givenfrom the fuel supply command means to the fuel supply means;

means for controlling an amount of a fuel supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means;

means for detecting an amount of the air supplied to the combustionchamber;

means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of the amount of the fuel estimated bythe fuel supply amount estimation means and the amount of the airdetected by the air amount detection means;

means for detecting the air-fuel ratio of the mixture gas formed in thecombustion chamber; and

means for performing an air-fuel ratio control for making the air-fuelratio of the mixture gas estimated by the air-fuel ratio estimationmeans and the air-fuel ratio of the mixture gas detected by the air-fuelratio detection means correspond to each other, using the estimated fuelsupply amount, the fuel supply command and the detected air amount orthe air supply command.

The device of this invention calculates on the basis of the differenceof the estimated air-fuel ratio relative to the detected air-fuel ratio,a correction value for correcting the amount estimated by the fuelsupply amount estimation means and the fuel supply command given to thefuel supply means to make the estimated and detected air-fuel ratioscorrespond to each other when the estimated and detected air-fuel ratiosdo not correspond to each other,

the device acquires as a fuel supply difference proportion, a rate ofthe air-fuel ratio difference due to the fuel supply difference of thefuel supply means occupying the air-fuel ratio difference and acquiresas an air amount detection difference proportion, a rate of the air-fuelratio difference due to the air amount detection difference of the airamount detection means occupying the air-fuel ratio difference,

calculates a correction value for correcting the estimated fuel supplyamount and the fuel supply command and a correction value for correctingthe detected air amount or the air supply command by dividing thecorrection value for the estimated fuel supply amount-fuel supplycommand correction, using the fuel supply and air amount detectiondifference proportions, and

controls the air-fuel ratio control using the estimated fuel supplyamount corrected by the correction value for fuel supply differencecompensation, the fuel supply command corrected by the correction valuefor the fuel supply difference compensation and the detected air amountor the air supply command corrected by the correction value for the airamount detection difference compensation.

In the device of this invention, in order to accomplish theabove-mentioned object, the correction value for the estimated fuelsupply amount-fuel supply command correction is divided to thecorrection value for the fuel supply difference compensation and thecorrection value for the air amount detection difference compensationsuch as the value equivalent to the air-fuel ratio difference calculatedusing the correction values for the fuel supply difference compensationand the air amount detection difference compensation corresponds to theair-fuel ratio difference.

According to this invention, the correction values for fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the air-fuel ratio difference whichis a difference of the estimated air-fuel ratio relative to the detectedair amount.

These correction values are set such that the air-fuel ratio differenceequivalent value equivalent to the air-fuel ratio difference calculatedfrom these correction values, becomes equal to the air-fuel ratiodifference (i.e. a value as the base of the setting of the correctionvalues for the fuel supply difference compensation and the air amountdetection difference compensation).

When the air-fuel ratio difference equivalent value is equal to theair-fuel ratio difference, the air-fuel ratio control using thesecorrection values is a control under the condition where the air-fuelratio difference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the air amountdetection difference.

Therefore, according to this invention, the effect obtained by thisair-fuel ratio control becomes high.

The air-fuel ratio difference of this invention may be any valueindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference equivalent valuecalculated by subtracting 1 from the ratio of the estimated air-fuelratio relative to the detected air-fuel ratio.

In this case, the correction value for the estimated fuel supplyamount/fuel supply command correction is calculated as a value formaking the difference equivalent value zero.

The method for obtaining the fuel supply difference and air amountdetection difference proportions is not limited to a particular methodand the following method may be preferred.

That is, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularamount when the air-fuel ratio control is performed using the estimatedfuel supply amount corrected by the correction value for the fuel supplydifference compensation, the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount or the air supply command not corrected by the airamount detection difference compensation under the condition where thefuel supply means has an error and the air amount detection means has noerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation, the fuel supplycommand not corrected by the correction value for the fuel supplydifference compensation and the detected air amount or the air supplycommand corrected by the air amount detection difference compensationunder the condition where the fuel supply means has an error and the airamount detection means has no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation, the fuel supply command correctedby the correction value for the fuel supply difference compensation andthe detected air amount or the air supply command not corrected by thecorrection value for the air amount detection difference compensationunder the condition where the fuel supply means has no error and the airamount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation, the fuel supplycommand not corrected by the correction value for the fuel supplydifference compensation and the detected air amount or the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas no error and the air amount detection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the fouracquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means) and the air amount detection means has an error (forexample, a drawing tolerance of the manufacturing of the air amountdetection means), the fuel supply difference and air amount detectiondifference proportions depending on the fuel supply difference of thefuel supply means and the air amount detection difference of the airamount detection means, are used for the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering the fuelsupply difference of the fuel supply means and the air amount detectiondifference of the air amount detection means and therefore, the effectobtained by the air-fuel ratio control becomes high.

For example, it is preferred that the fuel supply difference and airamount detection difference proportions are obtained as follows.

That is, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation, the fuel supply command correctedby the correction value for the fuel supply difference compensation andthe detected air amount or the air supply command not corrected by thecorrection value for the air amount detection difference compensationunder the condition where the fuel supply means has an error and the airamount detection means and the air-fuel ratio detection means have noerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation, the fuel supplycommand not corrected by the correction value for the fuel supplydifference compensation and the detected air amount or the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas an error and the air amount detection means and the air-fuel ratiodetection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation, the fuel supply command correctedby the correction value for the fuel supply difference compensation andthe detected air amount and the air supply command not corrected by thecorrection value for the air amount detection difference compensationunder the condition where the fuel supply means and the air-fuel ratiodetection means have no error and the air amount detection means has anerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount not corrected by the correctionvalue for the fuel supply difference compensation, the fuel supplycommand not corrected by the correction value for the fuel supplydifference compensation and the detected air amount or the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meansand the air-fuel ratio detection means have no error and the air amountdetection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation, the fuel supply command correctedby the correction value for the fuel supply difference compensation andthe detected air amount or the air supply command not corrected by thecorrection value for the air amount detection difference compensationunder the condition where the fuel supply means and the air amountdetection means have no error and the air-fuel ratio detection means hasan error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent when the air-fuel ratio control is performed using theestimated fuel supply amount not corrected by the correction value forthe fuel supply difference compensation, the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount or the air supply commandcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meansand the air amount detection means have no error and the air-fuel ratiodetection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetected difference proportions are obtained on the basis of the sixacquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means), the air amount detection means has an error (for example,a drawing tolerance of the manufacturing of the air amount detectionmeans) and the air-fuel ratio detection means has an error (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply difference and air amount detection differenceproportions depending on these differences of the fuel supply means, theair amount detection means and the air-fuel ratio detection means, areused for the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means, the air amount detection means and theair-fuel ratio detection means and therefore, the effect obtained by theair-fuel ratio control becomes high.

Further another invention of this application relates to a controldevice of an internal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying thefuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating an amount of the fuel supplied from the fuel supplymeans to the combustion chamber on the basis of the command given fromthe fuel supply command means to the fuel supply means;

means for controlling an amount of an air supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount by the air supply amount controlmeans to the combustion chamber;

means for detecting the amount of the air supplied to the combustionchamber;

means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of the amount of the air estimated bythe fuel supply amount estimation means and the amount of the airdetected by the air amount detection means;

means for detecting the air-fuel ratio of the mixture gas formed in thecombustion chamber; and

means for performing an air-fuel ratio control for making the air-fuelratios of the mixture gas estimated by the air-fuel ratio estimationmeans and detected by the air-fuel ratio detection means correspond toeach other, using the estimated fuel supply amount or the fuel supplycommand and the detected air amount.

The device of this invention calculates on the basis of the differenceof the estimated air-fuel ratio relative to the detected air-fuel ratio,a correction value for correcting the air amount detected by the airamount detection means to make the estimated and detected air-fuelratios correspond to each other when the estimated and detected air-fuelratios do not correspond to each other,

acquires as a fuel supply difference proportion, a rate of the air-fuelratio difference due to the fuel supply difference of the fuel supplymeans occupying the air-fuel ratio difference and acquires as an airamount detection difference proportion, a rate of the air-fuel ratiodifference due to the air amount detection difference of the air amountdetection means occupying the air-fuel ratio difference,

calculates a correction value for correcting the estimated fuel supplyamount or the fuel supply command and a correction value for correctingthe detected air amount by dividing the correction value for thedetected air amount correction, using the fuel supply difference and airamount detection difference proportions, and

performs the air-fuel ratio control using the estimated fuel supplyamount or the fuel supply command corrected by the correction value forthe fuel supply difference compensation and the detected air amountcorrected by the correction value for the air amount detectiondifference compensation.

In the device of this invention, in order to accomplish theabove-mentioned object, the correction value for the detected air amountcorrection is divided to the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation such that the air-fuel ratio difference equivalent valueequivalent to the air-fuel ratio difference calculated using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation, becomes equal to theair-fuel ratio difference.

According to this invention, the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the difference of the estimatedair-fuel ratio relative to the detected air-fuel ratio.

These correction values are set such that the air-fuel ratio differenceequivalent value equivalent to the air-fuel ratio difference calculatedfrom these correction values, becomes equal to the air-fuel ratiodifference (i.e. a value as the base of the setting of these correctionvalues).

When the air-fuel ratio difference equivalent value is equal to theair-fuel ratio difference, the air-fuel ratio control using thesecorrection values is a control under the condition where the air-fuelratio difference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the air amountdetection difference.

Therefore, according to this invention, the effect obtained by theair-fuel ratio control becomes high.

The air-fuel ratio difference of the invention may be any valuesindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference equivalent valuecalculated by subtracting 1 from the ratio of the estimated air-fuelratio relative to the detected air-fuel ratio.

In this case, the correction value for the detected air amountcorrection is calculated as a value for making the difference equivalentvalue zero.

The method for obtaining the fuel supply difference and air amountdetection difference proportions is not limited to a particular methodand the following method may be preferred.

That is, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has an error and the air amount detection means has noerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has an error and the air amountdetection means has no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has no error and the air amount detection means has anerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has no error and the air amountdetection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the fouracquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means) and the air amount detection means has an error (forexample, a drawing tolerance of the manufacturing of the air amountdetection means), the fuel supply difference and air amount detectiondifference proportions depending on the errors of the fuel supply meansand the air amount detection means, are used for the air-fuel ratiocontrol.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means and the air amount detection means andtherefore, the effect obtained by the air-fuel ratio control becomeshigh.

For example, it is preferred that the fuel supply difference and airamount detection difference proportions are obtained as follows.

That is, an amount of a particular component of an exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has an error and the air amount detection means andthe air-fuel ratio detection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has an error and the air amountdetection means and the air-fuel ratio detection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air-fuel ratio detection means have no errorand the air amount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means and the air-fuel ratio detectionmeans have no error and the air amount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air amount detection means have no error andthe air-fuel ratio detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command not corrected bythe correction value for the fuel supply difference compensation and thedetected air amount corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air amount detection means have no error and theair-fuel ratio detection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the sixacquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means), the air amount detection means has an error (for example,a drawing tolerance of the manufacturing of the air amount detectionmeans) and the air-fuel ratio detection means has an error (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply difference and air amount detection differenceproportions depending on the errors of the fuel supply means, the airamount detection means and the air-fuel ratio detection means, are usedfor the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means, the air amount detection means and theair-fuel ratio detection means and therefore, the effect obtained by theair-fuel ratio control becomes high.

Further another invention of this application relates to a controldevice of an internal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying thefuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating an amount of the fuel supplied from the fuel supplymeans to the combustion chamber on the basis of the command given fromthe fuel supply command means to the fuel supply means;

means for controlling an amount of an air supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means;

means for detecting the amount of the air supplied to the combustionchamber; means for estimating an air-fuel ratio of a mixture gas formedin the combustion chamber on the basis of the amount of the fuelestimated by the fuel supply amount estimation means and the amount ofthe air detected by the air amount detection means;

means for detecting the air-fuel ratio of the mixture gas formed in thecombustion chamber; and

means for performing an air-fuel ratio control for making the air-fuelratio of the mixture gas estimated by the air-fuel ratio estimationmeans and the air-fuel ratio of the mixture gas detected by the air-fuelratio detection means correspond to each other, using the estimated fuelsupply amount or the fuel supply command and the air supply command.

The device of this invention calculates on the basis of the differenceof the estimated air-fuel ratio relative to the detected air-fuel ratio,a correction value for correcting the command given to the air supplyamount control means to make the estimated and detected air-fuel ratioscorrespond to each other when the estimated and detected air-fuel ratiosdo not correspond to each other,

acquires as a fuel supply difference proportion, a rate of the air-fuelratio difference due to the fuel supply difference of the fuel supplymeans occupying the air-fuel ratio difference and acquires as an airamount detection difference proportion, a rate of the air-fuel ratiodifference due to the air amount detection difference of the air amountdetection means occupying the air-fuel ratio difference,

calculates a correction value for correcting the estimated fuel supplyamount or the fuel supply command and a correction value for correctingthe fuel supply command by dividing the correction value for the airsupply command correction, using the fuel supply difference and airamount detection difference proportions, and

performs the air-fuel ratio control using the estimated fuel supplyamount or the fuel supply command corrected by the correction value forthe fuel supply difference compensation and the air supply commandcorrected by the correction value for the air amount detectiondifference compensation.

In the device of this invention, in order to accomplish theabove-mentioned object, the correction value for the air supply commandcorrection is divided to the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation such that the air-fuel ratio difference equivalent valueequivalent to the air-fuel ratio difference calculated using thecorrection values for the fuel supply difference compensation and theair amount detection compensation, becomes equal to the air-fuel ratiodifference.

According to this invention, the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the difference of the estimatedair-fuel ratio relative to the detected air-fuel ratio.

These correction values are set such that the air-fuel ratio differenceequivalent value equivalent to the air-fuel ratio difference calculatedfrom these correction values, becomes equal to the air-fuel ratiodifference (i.e. a value as the base of the setting of these correctionvalues).

When the air-fuel ratio difference equivalent value is equal to theair-fuel ratio difference, the air-fuel ratio control using thesecorrection values is a control under the condition where the air-fuelratio difference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the air amountdetection difference.

Therefore, according to this invention, the effect obtained by theair-fuel ratio control becomes high.

The air-fuel ratio difference of the invention may be any valuesindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference calculated bysubtracting 1 from the ratio of the estimated air-fuel ratio relative tothe detected air-fuel ratio.

In this case, the correction value for the air supply command correctionis calculated as a value for making the difference equivalent valuezero.

The method for obtaining the fuel supply difference and air amountdetection difference proportions is not limited to a particular methodand the following method may be preferred.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has an error and the air amount detection means has noerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the air supply command corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has an error and the air amountdetection means has no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has no error and the air amount detection means has anerror.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the air supply command corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has no error and the air amountdetection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the fouracquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means) and the air amount detection means has an error (forexample, a drawing tolerance of the manufacturing of the air amountdetection means), the fuel supply difference and air amount detectiondifference proportions depending on the errors of the fuel supply meansand the air amount detection means, are used for the air-fuel ratiocontrol.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means and the air amount detection means andtherefore, the effect obtained by the air-fuel ratio control becomeshigh.

For example, it is preferred that the fuel supply difference and airamount detection difference proportions are obtained as follows.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means has an error and the air amount detection means and theair-fuel ratio detection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the air supply command corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means has an error and the air amountdetection means and the air-fuel ratio detection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air-fuel ratio detection means have no error andthe air amount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation and the air supply command corrected by the correctionvalue for the air amount detection difference compensation under thecondition where the fuel supply means and the air-fuel ratio detectionmeans have no error and the air amount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and the airsupply command not corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air amount detection means have no error and theair-fuel ratio detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command not corrected bythe correction value for the fuel supply difference compensation and theair supply command corrected by the correction value for the air amountdetection difference compensation under the condition where the fuelsupply means and the air amount detection means have no error and theair-fuel ratio detection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the sixacquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means), the air amount detection means has an error (for example,a drawing tolerance of the manufacturing of the air amount detectionmeans) and the air-fuel ratio detection means has an error (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply difference and air amount detection differenceproportions depending on the errors of the fuel supply means, the airamount detection means and the air-fuel ratio detection means, are usedfor the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means, the air amount detection means and theair-fuel ratio detection means and therefore, the effect obtained by theair-fuel ratio control becomes high.

Further another invention of this application relates to a controldevice of an internal combustion engine, comprising:

means for supplying a fuel to a combustion chamber;

means for giving to the fuel supply means, a command for supplying thefuel of a target amount to the combustion chamber by the fuel supplymeans;

means for estimating an amount of the fuel supplied to the combustionchamber from the fuel supply means on the basis of the command given tothe fuel supply means from the fuel supply command means;

means for controlling an amount of an air supplied to the combustionchamber;

means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means;

means for detecting the amount of the air supplied to the combustionchamber;

means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of the amount of the fuel estimated bythe fuel supply amount estimation means and the amount of the airdetected by the air amount detection means; means for detecting theair-fuel ratio of the mixture gas formed in the combustion chamber; and

means for performing an air-fuel ratio control for making the air-fuelratios of the mixture gas estimated by the air-fuel ratio estimationmeans and detected by the air-fuel ratio detection means correspond toeach other, using the estimated fuel supply amount or the fuel supplycommand, the detected air amount and the air supply command.

The device of this invention calculates on the basis of the differenceof the estimated air-fuel ratio relative to the detected air-fuel ratio,a correction value for correcting the air amount detected by the airamount detection means and the command given to the air supply amountcontrol means to make the estimated and detected air-fuel ratioscorrespond to each other when the estimated and detected air-fuel ratiosdo not correspond to each other,

acquires as a fuel supply difference proportion, a rate of the air-fuelratio difference due to the fuel supply difference of the fuel supplymeans occupying the air-fuel ratio difference and acquires as an airamount detection difference proportion, a rate of the air-fuel ratiodifference due to the air amount detection difference of the air amountdetection means occupying the air-fuel ratio difference,

calculates a correction value for correcting the estimated fuel supplyamount or the fuel supply command and a correction value for correctingthe detected air amount and the air supply command by dividing thecorrection value for the detected air amount/air supply commandcorrection, using these rates, and

performs the air-fuel ratio control using the estimated fuel supplyamount or the fuel supply command corrected by the correction value forthe fuel supply difference compensation, the detected air amountcorrected by the correction value for the air amount detectiondifference compensation and the air supply command corrected by thecorrection value for the air amount detection difference compensation.

In the device of this invention, in order to accomplish theabove-mentioned object, the correction value for the detected airamount/air supply command correction is divided to the correction valuesfor the fuel supply difference compensation and the air amount detectiondifference compensation such that the air-fuel ratio equivalent valueequivalent to the air-fuel ratio difference calculated using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation, becomes equal to theair-fuel ratio difference.

According to this invention, the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation are set on the basis of the difference of the estimatedair-fuel ratio relative to the detected air-fuel ratio.

These correction values are set such that the air-fuel ratio differenceequivalent value equivalent to the air-fuel ratio difference calculatedfrom these correction values, becomes equal to the air-fuel ratiodifference (i.e. a value as the base of the setting of these correctionvalues).

When the air-fuel ratio difference equivalent value is equal to theair-fuel ratio difference, the air-fuel ratio control using thesecorrection values is a control under the condition where the air-fuelratio difference is distributed appropriately to the air-fuel ratiodifferences due to the fuel injection difference and the air amountdetection difference.

Therefore, according to this invention, the effect obtained by theair-fuel ratio control becomes high.

The air-fuel ratio difference of the invention may be any valuesindicating the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio and may be a difference equivalent valuecalculated by subtracting 1 from the ratio of the estimated air-fuelratio relative to the detected air-fuel ratio.

In this case, the correction value for the detected air amount/airsupply command correction is calculated as a value for making thedifference equivalent value zero.

The method for obtaining the fuel supply difference and air amountdetection difference proportions is not limited to a particular methodand the following method may be preferred.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation, thedetected air amount not corrected by the correction value for the airamount detection difference compensation and the air supply command notcorrected by the air amount detection difference compensation under thecondition where the fuel supply means has an error and the air amountdetection means has no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation, the detected air amount corrected by the correction valuefor the air amount detection difference compensation and the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas an error and the air amount detection means has no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation, thedetected air amount not corrected by the correction value for the airamount detection difference compensation and the air supply command notcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas no error and the air amount detection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation, the detected air amount corrected by the correction valuefor the air amount detection difference compensation and the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas no error and the air amount detection means has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the fouracquired particular component amounts.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means) and the air amount detection means has an error (forexample, a drawing tolerance of the manufacturing of the air amountdetection means), the fuel supply difference and air amount detectiondifference proportions depending on the errors of the fuel supply meansand the air amount detection means, are used for the air-fuel ratiocontrol.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means and the air amount detection means andtherefore, the effect obtained by the air-fuel ratio control becomeshigh.

For example, it is preferred that the fuel supply difference and airamount detection difference proportions are obtained as follows.

That is, an amount of a particular component of the exhaust gasdischarged from the combustion chamber is acquired as a first particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation, thedetected air amount not corrected by the correction value for the airamount detection difference compensation and the air supply command notcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas an error and the air amount detection means and the air-fuel ratiodetection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a secondparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation, the detected air amount corrected by the correction valuefor the air amount detection difference compensation and the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas an error and the air amount detection means and the air-fuel ratiodetection means have no error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a third particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation, thedetected air amount not corrected by the correction value for the airamount detection difference compensation and the air supply command notcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meansand the air-fuel ratio detection means have no error and the air amountdetection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fourthparticular component amount when the air-fuel ratio control is performedusing the estimated fuel supply amount or the fuel supply command notcorrected by the correction value for the fuel supply differencecompensation, the detected air amount corrected by the correction valuefor the air amount detection difference compensation and the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meansand the air-fuel ratio detection means have no error and the air amountdetection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a fifth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation, thedetected air amount not corrected by the correction value for the airamount detection difference compensation and the air supply command notcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meansand the air amount detection means have no error and the air-fuel ratiodetection means has an error.

Further, an amount of the particular component of the exhaust gasdischarged from the combustion chamber is acquired as a sixth particularcomponent amount when the air-fuel ratio control is performed using theestimated fuel supply amount or the fuel supply command not corrected bythe correction value for the fuel supply difference compensation, thedetected air amount corrected by the correction value for the air amountdetection difference compensation and the air supply command correctedby the correction value for the air amount detection differencecompensation under the condition where the fuel supply means and the airamount detection means have no error and the air-fuel ratio detectionmeans has an error.

Then, it is preferred that the fuel supply difference and air amountdetection difference proportions are obtained on the basis of the sixacquired particular component amount.

According to this invention, when the fuel supply means has an error(for example, a drawing tolerance of the manufacturing of the fuelsupply means), the air amount detection means has an error (for example,a drawing tolerance of the manufacturing of the air amount detectionmeans) and the air-fuel ratio detection means has an error (for example,a drawing tolerance of the manufacturing of the air-fuel ratio detectionmeans), the fuel supply difference and air amount detection differenceproportions depending on the errors of the fuel supply means, the airamount detection means and the air-fuel ratio detection means, are usedfor the air-fuel ratio control.

Therefore, the air-fuel ratio control is performed considering theerrors of the fuel supply means, the air amount detection means and theair-fuel ratio detection means therefore, the effect obtained by theair-fuel ratio control becomes high.

When the device of the invention further comprises an exhaust gasrecirculation means for introducing into an intake passage, an exhaustgas discharged from the combustion chamber to an exhaust passage, atarget amount of the exhaust gas introduced into the intake passage bythe exhaust gas recirculation means may be determined on the basis ofthe estimated fuel supply amount and the estimated fuel supply amountcorrected by the correction value for the fuel supply differencecompensation may be used for the determination of the target amount.

When the device of the invention further comprises means for estimatingan actual amount of the exhaust gas introduced actually into the intakepassage by the exhaust gas recirculation means, using the detected airamount, the detected air amount corrected by the correction value forthe air amount detection difference compensation may be used for theestimation of the actual recirculated exhaust gas amount by the actualrecirculated exhaust gas amount estimation means.

In the invention, the amount of the exhaust gas introduced into theintake passage by the exhaust gas recirculation means may be controlledsuch that the actual amount estimated by the actual recirculated exhaustgas amount estimation means corresponds to the target amount.

When the device of the invention further comprises means for detectingan amount of a particular component of the exhaust gas discharged fromthe combustion chamber, the fuel supply difference and air amountdetection difference proportions may be employed as follows.

That is, a base of the fuel supply difference proportion is set as abase fuel supply difference proportion, the air amount detectiondifference proportion corresponding to this base rate is set as a baseair amount detection difference proportion and an amount of theparticular component of the exhaust gas discharged from the combustionchamber is acquired as a base particular component amount by theparticular component amount detection means when the air-fuel ratiocontrol is performed using these base rates.

A rate larger than the base fuel supply difference proportion is set asa first comparison fuel supply difference proportion, the air amountdetection difference proportion corresponding to this first rate is setas a first comparison air amount detection difference proportion, and anamount of the particular component of the exhaust gas discharged fromthe combustion chamber is acquired as a first comparison particularcomponent amount by the particular component amount detection means whenthe air-fuel ratio control is performed using these first rates.

Further, a rate smaller than the base fuel supply difference proportionis set as a second comparison fuel supply difference proportion, theair-fuel ratio detection difference proportion corresponding to thissecond rate is set as a second comparison air amount detectiondifference proportion, and an amount of the particular component of theexhaust gas discharged from the combustion chamber is acquired as asecond comparison particular component amount by the particularcomponent amount detection means when the air-fuel ratio control isperformed using these second rates.

When the base particular component amount is the smallest among theacquired particular component amounts, the base fuel supply differenceand base air amount detection difference proportions are employed as thefuel supply difference and air amount detection difference proportions,respectively.

On the other hand, a first process is performed when the firstcomparison particular component amount is the smallest among theacquired particular component amounts, the process comprising:

setting the first comparison fuel supply difference and first comparisonair amount detection difference proportions as new base fuel supplydifference and base air amount detection difference proportions,respectively,

acquiring an amount of the particular component of the exhaust gasdischarged from the combustion chamber as a base particular componentamount by the particular component amount detection means when theair-fuel ratio control is performed using these new rates,

setting a rate larger than the new base fuel supply differenceproportion as a new first comparison fuel supply difference proportion,

setting the air amount detection difference proportion corresponding tothis first rate as a new first comparison air amount detectiondifference proportion,

acquiring an amount of the particular component of the exhaust gasdischarged from the combustion chamber as a first comparison particularcomponent amount by the particular component amount detection means whenthe air-fuel ratio control is performed using these new first rates,

setting a rate smaller than the new base fuel supply differenceproportion as a new second comparison fuel supply difference proportion,

setting the air amount detection difference proportion corresponding tothis second rate as a new second comparison air amount detectiondifference proportion, and

acquiring an amount of the particular component of the exhaust gasdischarged from the combustion chamber as a second comparison particularcomponent amount by the particular component amount detection means whenthe air-fuel ratio control is performed using these new second rates.

On the other hand, a second process is performed when the secondcomparison particular component amount is the smallest among theacquired particular component amounts, the second process comprising:

setting the second comparison fuel supply difference and secondcomparison air amount detection difference proportions as new base fuelsupply difference and base air amount detection difference proportions,respectively,

acquiring as a base particular component amount by the particularcomponent amount detection means, an amount of the particular componentof the exhaust gas discharged from the combustion chamber when theair-fuel ratio control is performed using these new base rates,

setting a rate larger than the new base fuel supply differenceproportion as a new first comparison fuel supply difference proportion,

setting the air amount detection difference proportion corresponding tothis first comparison fuel supply difference proportion as a new firstcomparison air amount detection difference proportion,

acquiring as a first comparison particular component amount by theparticular component amount detection means, an amount of the particularcomponent of the exhaust gas discharged from the combustion chamber whenthe air-fuel ratio control is performed using these new first rates,

setting a rate smaller than the new base fuel supply differenceproportion as a second comparison fuel supply difference proportion,

setting the air amount detection difference proportion corresponding tothis second comparison fuel difference proportion as a new secondcomparison air amount detection difference proportion, and

acquiring as a second comparison particular component amount by theparticular component amount detection means, an amount of the particularcomponent of the exhaust gas discharged from the combustion chamber whenthe air-fuel ratio control is performed using these new secondcomparison rates.

The first process is performed when the first comparison particularcomponent amount is the smallest among the particular component amountsacquired by the first and second processes,

the second process is performed when the second comparison particularcomponent amount is the smallest among the particular component amountsacquired by the first and second processes, and

the base fuel supply difference and base air amount detection differenceproportions used in the first and second processes are employed as thefuel supply difference and air amount detection difference proportions,respectively when the base particular component amount is the smallestamong the particular component amounts acquired by the first and secondprocesses.

When the fuel supply difference occurs in the fuel supply means due tothe deterioration thereof or the difference changes, or when the airamount detection difference occurs in the air amount detection means dueto the deterioration thereof or the difference changes, or when theair-fuel ratio detection difference occurs in the air-fuel ratiodetection means due to the deterioration thereof or the differencechanges, the suitable fuel supply difference and air amount detectiondifference proportions also change.

According to this invention, even when such differences occur or change,during the engine operation, the suitable fuel supply difference and airamount detection difference proportions are employed and the effectobtained by the air-fuel ratio control becomes high.

In the invention, a range allowable as the correction value for the fuelsupply difference compensation may be previously set as a fuel supplydifference allowable range and when the correction value for the fuelsupply difference compensation is not within the range, it may be judgedthat a malfunction occurs in the fuel supply means.

According to this invention, even when the fuel supply difference occursin the fuel supply means due to the deterioration thereof or thedifference changes or even when the air amount detection differenceoccurs in the air amount detection means due to the deteriorationthereof or the difference changes or even when the air-fuel ratiodetection difference occurs in the air-fuel ratio detection means due tothe deterioration thereof or the difference changes, the malfunctiondiagnosis of the fuel supply means is performed using the correctionvalue for the fuel supply difference compensation calculated on thebasis of the suitable fuel supply difference proportion.

Therefore, according to this invention, the malfunction of the fuelsupply means is exactly diagnosed.

In the invention, a range allowable as the correction value for the airamount detection difference compensation may be previously set as an airamount detection difference allowable range and when the correctionvalue for the air amount detection difference compensation is not withinthe range, it may be judged that the malfunction occurs in the airamount detection means.

According to this invention, even when the fuel supply difference occursin the fuel supply means due to the deterioration thereof or thedifference changes, or even when the air amount detection differenceoccurs in the air amount detection means due to the deteriorationthereof or the difference changes, or even when the air-fuel ratiodetection difference occurs in the air-fuel ratio detection means due tothe deterioration thereof or the difference changes, the malfunctiondiagnosis of the air amount detection means is performed using thecorrection value for the air amount detection difference compensationcalculated on the basis of the suitable air amount detection differenceproportion.

Therefore, according to this invention, the malfunction of the airamount detection means is exactly diagnosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view showing an internal combustion engine which acontrol device of this invention applies.

FIG. 2(A) is a view showing a map used for acquiring a target fuelinjection amount TQ on the basis of an accelerator pedal opening degreeDac in one embodiment of this invention, FIG. 2(B) is a view showing amap used for acquiring a target throttle valve opening degree TDth onthe basis of a fuel injection amount Q and an engine speed N in oneembodiment of this invention and FIG. 2(C) is a view showing a map usedfor acquiring a target EGR rate TRegr on the basis of the fuel injectionamount Q and the engine speed N in one embodiment of this invention.

FIG. 3 is a view showing a map used for acquiring a learned value KG onthe basis of the fuel injection amount Q and the engine speed N in oneembodiment of this invention.

FIG. 4 is a flowchart showing an example of a routine for performing acontrol of a fuel injector of this invention.

FIG. 5 is a flowchart showing an example of a routine for performing acontrol of a throttle valve of this invention.

FIG. 6 is a flowchart showing an example of a routine for performing acontrol of an EGR control valve of this invention.

FIG. 7 is a flowchart showing an example of a routine for performing acalculation of correction values for a target fuel injection amountcorrection and a detected fresh air amount correction and an update of alearned correction value of this invention.

FIG. 8 is a view for explaining one embodiment of a setting of adistribution coefficient of this invention.

FIG. 9(A) is a view showing a first distribution coefficient map andFIG. 9(B) is a view showing a second distribution coefficient map.

FIG. 10 is a flowchart showing an example of a routine for performing asetting of a distribution coefficient of another embodiment of thisinvention.

FIG. 11 is a flowchart showing an example of a routine for performing amalfunction diagnosis of the fuel injector of this invention.

FIG. 12 is a flowchart showing an example of a routine for performing amalfunction diagnosis of an air flow meter of this invention.

MODE FOR CARRYING OUT THE INVENTION

Below, an embodiment of a control device of an internal combustionengine of the invention will be explained referring to the drawings. Aninternal combustion chamber which a control device of this inventionapplies is shown in FIG. 1.

The engine 10 shown in FIG. 1 comprises a body 20 of the engine(hereinafter, this body will be referred to as—engine body—), fuelinjectors 21 arranged corresponding to four combustion chambers of theengine body, respectively, and a fuel pump 22 for supplying a fuel tothe fuel injectors 21 via a fuel supply pipe 23.

The engine 10 further comprises an intake system 30 for supplying an airfrom the outside to the combustion chambers and an exhaust system 40 fordischarging to the outside an exhaust gas discharged from the combustionchamber,

The engine 10 is a compression self-ignition internal combustion engine(so-called diesel engine).

It should be noted that the fuel injector 21 supplies the fuel to thecombustion chamber by injecting the fuel into the combustion chamber.Therefore, it can be said that the fuel injector 21 is means forsupplying the fuel to the combustion chamber.

The intake system 30 has intake branch pipes 31 and an intake pipe 32.In the following explanation, the intake system 30 will be also referredto as—intake passage—.

One of ends (i.e. branch portion) of the intake branch pipe 31 isconnected to an intake port (now shown) formed in the engine body 20corresponding to each combustion chamber. On the other hand, the otherend of the intake branch pipe 31 is connected to the intake pipe 32.

A throttle valve 33 for controlling an amount of the air flowing in theintake pipe is arranged in the intake pipe 32.

Further, an intercooler 34 for cooling the air flowing in the intakepipe is arranged in the intake pipe 32.

Further, an air cleaner 36 is arranged in an end of the intake pipe 32which opens to the outside.

The throttle valve 33 can control the amount of the air sucked into thecombustion chamber by the operation condition thereof (concretely, theopening degree thereof and hereinafter, this opening degree will bereferred to as—throttle valve opening degree—) being controlled. Thatis, the throttle valve 33 can control the amount of the air supplied tothe combustion chamber.

Therefore, it can be said that the throttle valve 33 is means forcontrolling the amount of the air supplied to the combustion chamber.

On the other hand, the exhaust system 40 has exhaust branch pipes 41 andan exhaust pipe 42. In the following explanation, the exhaust system 40will be also referred to as—exhaust passage—.

One of ends (i.e. branch portions) of the exhaust branch pipe 41 isconnected to an exhaust port (not shown) formed in the engine body 20corresponding to each combustion chamber. On the other hand, the otherend of the exhaust branch pipe 41 is connected to the exhaust pipe 42.

A catalyst converter 43 incorporating an exhaust purification catalyst43A for purifying a specific component(s) in the exhaust gas is arrangedin the exhaust pipe 42.

An oxygen concentration sensor 76U for outputing a signal correspondingto the oxygen concentration in the exhaust gas discharged from thecombustion chamber is mounted on the exhaust pipe 42 upstream of theexhaust purification catalyst 43A (hereinafter, this oxygenconcentration sensor will be referred to as—upstream oxygenconcentration sensor—).

On the other hand, an oxygen concentration sensor 76D for outputting asignal corresponding to the oxygen concentration in the exhaust gasflowing out of the exhaust purification catalyst 43A is mounted on theexhaust pipe 42 downstream of the exhaust purification catalyst 43A(hereinafter, this oxygen concentration sensor will be referred toas—downstream oxygen concentration sensor—).

An air flow meter 71 for outputting a signal corresponding to the flowrate of the air flowing in the intake pipe (therefore, the flow rate ofthe air sucked into the combustion chamber and hereinafter, this flowrate will be referred to as—fresh air amount—) is mounted on the intakepipe 32 downstream of the air cleaner 36.

A pressure sensor 72 for outputting a signal corresponding to thepressure of the gas in the intake branch pipe (i.e. the intake pressure)is mounted on the intake branch pipe 31 (hereinafter, this sensor willbe referred to as—intake pressure sensor—).

A crank position sensor 74 for outputting a signal corresponding to therotation phase of the crank shaft is mounted on the engine body 20.

The engine 10 further comprises an exhaust recirculation device(hereinafter, this device will be referred to as—EGR device—) 50. TheEGR device 50 has an exhaust recirculation pipe (hereinafter, this pipewill be referred to as—EGR passage—) 51.

One end of the EGR passage 51 is connected to the exhaust branch pipe41. On the other hand, the other end of the EGR passage 51 is connectedto the intake branch pipe 31. That is, the other end of the EGR passage51 is connected to the portion of the intake passage downstream of thethrottle valve 33.

An exhaust recirculation control valve (hereinafter, this valve will bereferred to as—EGR control valve—) 52 for controlling the flow rate ofthe exhaust gas flowing in the EGR passage is arranged in the EGRpassage 51.

In the engine 10, as the opening degree of the EGR control valve 52(hereinafter, this opening degree will be referred to as—EGR controlvalve opening degree—) is large, the flow rate of the exhaust gasflowing in the EGR passage 51 is large.

An exhaust recirculation cooler 53 for cooling the exhaust gas flowingin the EGR passage is arranged on the EGR passage 51.

The EGR device 50 can control the amount of the exhaust gas introducedinto the intake passage 30 via the EGR passage 51 (hereinafter, thisexhaust gas will be referred to as—EGR gas—) by the operation conditionof the EGR control valve 52 (concretely, the opening degree of the EGRcontrol valve 52 and hereinafter, this opening degree will be referredto as—EGR control valve opening degree—) being controlled.

The engine 10 further comprises electronic control unit 60. Theelectronic control unit 60 has a microprocessor (CPU) 61, a read onlymemory (ROM) 62, a random access memory (RAM) 63, a back-up RAM 64, andan interface 65.

The fuel injectors 21, the fuel pump 22, the throttle valve 33, and theEGR control valve 52 are connected to the interface 65 and the controlsignals for controlling the operation thereof are given from theelectronic control unit 60 via the interface 65.

Also, the air flow meter 71, the intake pressure sensor 72, the crankposition sensor 74, an accelerator pedal opening degree sensor 75 foroutputting a signal corresponding to the opening degree of theaccelerator pedal AP (i.e. the depression amount of the acceleratorpedal AP and hereinafter, this opening degree will be referred toas—accelerator pedal opening degree—), and the upstream and downstreamoxygen concentration sensors 76U and 76D are connected to the interface65, and the signals output from the air flow meter 71, the intakepressure sensor 72, the crank position sensor 74, the accelerator pedalopening degree sensor 75, and the upstream and downstream oxygenconcentration sensors 76U and 76D are input to the interface 65.

The fresh air amount is calculated by the electronic control unit 60 onthe basis of the signal output from the air flow meter 71 (hereinafter,this fresh air amount will be referred to as—detected fresh airamount—), the intake pressure is calculated by the electronic controlunit 60 on the basis of the signal output from the intake pressuresensor 72, the engine speed (i.e. speed of the engine 10) is calculatedby the electronic control unit 60 on the basis of the signal output fromthe crank position sensor 74, the accelerator pedal opening degree iscalculated by the electronic control unit 60 on the basis of the signaloutput from the accelerator pedal opening degree sensor 75, the air-fuelratio of the exhaust gas discharged from the combustion chamber iscalculated by the electronic control unit 60 on the basis of the signaloutput from the upstream oxygen concentration sensor 76U, and theair-fuel ratio of the exhaust gas flowing out of the exhaustpurification catalyst 43A is calculated by the electronic control unit60 on the basis of the signal output from the downstream oxygenconcentration sensor 760.

Therefore, it can be said that the air flow meter 71 functions as meansfor detecting the fresh air amount, the intake pressure sensor 72functions as means for detecting the intake pressure, the crank positionsensor 74 functions as means for detecting the engine speed, theaccelerator pedal opening degree sensor 75 functions as means fordetecting the accelerator pedal opening degree, the upstream oxygenconcentration sensor 76U functions as means for detecting the oxygenconcentration in the exhaust gas discharged from the combustion chamber,and the downstream oxygen concentration sensor 76D functions as meansfor detecting the oxygen concentration in the exhaust gas flowing out ofthe exhaust purification catalyst 43A.

Further, as the intake pressure is high, the amount of the gas suckedinto the combustion chamber is large and as the intake pressure is low,the amount of the gas sucked into the combustion chamber is small.

Then, the intake pressure sensor 72 functions as means for detecting theintake pressure and therefore, the amount of the gas sucked into thecombustion chamber can be grasped on the basis of the intake pressuredetected by the sensor 72.

Therefore, it can be said that the intake pressure sensor 71 functionsas means for detecting the amount of the gas sucked into the combustionchamber.

Further, as the air-fuel ratio of the mixture gas is large, the oxygenconcentration in the burned gas produced by the combustion of themixture gas formed in the combustion chamber is high and as the air-fuelratio of the mixture gas is small, the oxygen concentration is low.

Further, in the case that the oxygen concentration in the burned gasproduced by the combustion chamber when the mixture gas having thestoichiometric air-fuel ratio burns in the combustion chamber isreferred to as base oxygen concentration, the oxygen concentration inthe burned gas produced by the combustion of the mixture formed in thecombustion chamber is larger than the base oxygen concentration when theair-fuel ratio of the mixture is larger than the stoichiometric air-fuelratio while the oxygen concentration is smaller than the base oxygenconcentration when the air-fuel ratio of the mixture is smaller than thestoichiometric air-fuel ratio.

Then, the upstream oxygen concentration sensor 76U functions as meansfor detecting the oxygen concentration in the exhaust gas dischargedfrom the combustion chamber and therefore, the air-fuel ratio of themixture gas can be grasped on the basis of the oxygen concentrationdetected by this sensor 76U.

Therefore, it can be said that the sensor 76U functions as means fordetecting the air-fuel ratio of the mixture gas.

Next, an embodiment of the invention relating to the control of the fuelinjector will be explained.

In one embodiment of the invention, a suitable fuel injection amount(i.e. the amount of the fuel injected from the fuel injector) dependingon each accelerator pedal opening degree in the engine shown in the FIG.1 is previously obtained by an experiment, etc, and the obtained fuelinjection amounts are memorized as target fuel injection amounts TQ inthe electronic control unit 60 in the form of a map as a function of theaccelerator pedal opening degree Dac as shown in FIG. 2(A).

Then, during the engine operation (i.e. during the operation of theengine), a target fuel injection amount TQ is acquired from the mapshown in FIG. 2(A) on the basis of the accelerator pedal opening degreeDac.

Then, a fuel injector opening period (i.e. the period to open the fuelinjector to inject the fuel from the fuel injector) necessary to injectthe fuel having this acquired target fuel injection amount TQ from thefuel injector is calculated on the basis of this target fuel injectionamount TQ.

Then, the opening period of the fuel injector is controlled at eachintake stroke so as to open the fuel injector for this calculated fuelinjector opening period.

In the map shown in FIG. 2(A), as the accelerator pedal opening degreeDac is large, the target fuel injection amount TQ is large.

Next, an embodiment of the invention relating to the control of thethrottle valve will be explained.

In one embodiment of the invention, a suitable throttle valve openingdegree (i.e. the opening degree of the throttle valve) depending on eachcombination of the fuel injection amount and the engine speed (i.e. thespeed of the engine) in the engine shown in FIG. 1 is previouslyobtained by an experiment, etc, and the obtained throttle valve openingdegrees are memorized as target throttle valve opening degree TDth inthe electronic control unit 60 as a form of the map as a function of thefuel injection amount Q and the engine speed N as shown in FIG. 2(B).

Then, during the engine operation, a target throttle valve openingdegree TDth is acquired from the map shown in FIG. 2(B) on the basis ofthe fuel injection amount Q and the engine speed N.

Then, the throttle valve opening degree is controlled to open thethrottle valve for this acquired target throttle valve opening degreeTDth.

In the map shown in FIG. 2(B), as the fuel injection amount Q is large,the throttle valve opening degree TDth is large, and as the engine speedN is large, the target throttle valve opening degree TDth is large.

Further, in this embodiment, the target fuel injection amount TQ (i.e.the target fuel injection amount TQ acquired from the map shown in FIG.2(A)) is employed as the fuel injection amount Q used for acquiring thetarget throttle valve opening degree TDth from the map shown in FIG.2(B).

Next, an embodiment of the invention relating to the control of the EGRcontrol valve will be explained.

In one embodiment of the invention, a suitable EGR rate (i.e. a ratio ofthe mass of the exhaust gas included in the gas sucked into thecombustion chamber) depending on each combination of the fuel injectionamount and the engine speed is previously obtained by an experiment,etc, and the obtained EGR rates are memorized as target EGR rates TRegrin the electronic control unit 60 in the form of a map as a function ofthe fuel injection amount Q and the engine speed N as shown in FIG.2(C).

Then, during the engine operation, a target EGR rate TRegr is acquiredfrom the map shown in FIG. 2(C) on the basis of the fuel injectionamount Q and the engine speed N.

In the map shown in FIG. 2(C), as the fuel injection amount Q is large,the target EGR rate TRegr is small and as the engine speed is large, thetarget EGR rate TRegr is small.

On the other hand, during the engine operation, an estimated value ofthe actual EGR rate RegrE is calculated according to the followingformula 1 (hereinafter, this estimated value will be referred toas—estimated EGR rate—).

In the formula 1, “Gc” is an in-cylinder intake gas amount (i.e. anamount of the gas sucked into the combustion chamber (i.e. the mixed gasof the air and the EGR gas)), “Ga” is the detected fresh air amount and“KGa” is a correction value for the detected fresh air amountcorrection.

RegrE=(Gc−Ga×Kga)/Gc  (1)

Then, an EGR rate difference (i.e. a difference of the actual EGR raterelative to the target EGR rate) is calculated according to thefollowing formula 2.

In the formula 2, “TRegr” is the target EGR rate acquired from the mapshown in FIG. 2(C) and “RegrE” is the estimated EGR rate calculatedaccording to the formula 1.

ΔRegr=TRegr−RegrE  (2)

Then, the EGR control valve opening degree (i.e. the opening degree ofthe EGR control valve) is controlled by the feedback control such thatthe EGR rate difference ΔRegr calculated according to the formula 2becomes zero.

Next, an embodiment of the invention relating to the calculation of thein-cylinder intake gas amount will be explained. In one embodiment ofthe invention, the in-cylinder intake gas amount Gc is calculatedaccording to the following formula 3.

In the formula 3, “Pim” is the intake pressure, “N” is the engine speedand “F” is a function for calculating the in-cylinder intake gas amounton the basis of the intake pressure and the engine speed.

Gc=F(Pim,N)  (3)

Next, an embodiment of the invention relating to the calculation of thefuel injection amount Q used for acquiring the target EGR rate TRegrfrom the map shown in FIG. 2(C) will be explained (hereinafter, thisfuel injection amount will be referred to as—fuel injection amount forthe target EGR rate acquisition—).

In one embodiment of the invention, the fuel injection amount Q for thetarget EGR rate acquisition is calculated according to the followingformula 4.

In the formula 4, “TQ” is the target fuel injection amount acquired fromthe map shown in FIG. 2(A) and “Kq” is a correction value for the targetfuel injection amount correction.

Q=TQ×KQ  (4)

Next, an embodiment of the invention relating to the calculation of thefresh air amount Ga used for calculating the estimated EGR rate RegrEaccording to the formula 1 will be explained (hereinafter, this freshair amount will be explained as to—fresh air amount for the estimatedEGR rate calculation—).

In one embodiment of the invention, the fresh air amount Ga for theestimated EGR rate calculation is calculated according to the followingformula 5.

In the formula 5, “Gad” is the detected fresh air amount and “Kga” is acorrection value for the detected fresh air amount correction.

Ga=Gad×Kga  (5)

Next, an embodiment of the invention relating to the calculation of thecorrection value for the target fuel injection amount correction used inthe formula 4 will be explained.

In one embodiment of the invention, the correction value Kq for thetarget fuel injection amount correction is calculated according to thefollowing formula 6.

In the formula 6, “Kb” is a base correction value which will beexplained later in detail and “Kd” is a coefficient for distributing thebase correction value into the correction values for the target fuelinjection amount correction and the detected fresh air amount correction(hereinafter, this coefficient will be referred to as—distributioncoefficient—).

Kq=KbKd  (6)

Next, an embodiment of the invention relating to the calculation of thecorrection value for the detected fresh air amount correction used inthe formula 5 will be explained.

In one embodiment of the invention, the correction value Kga for thedetected fresh air amount correction is calculated according to thefollowing formula 7.

In the formula 7, “Kb” is the base correction value which will beexplained later in detail and “Kd” is the distribution coefficient.

Kga=Kb−(1−Kd)  (7)

Next, an embodiment of the invention relating to the calculation of thebase correction value Kb will be explained. In one embodiment of theinvention, an estimated air-fuel ratio AFe is calculated according tothe following formula 8.

In the formula 8, “Ga” is the detected fresh air amount, “TQ” is thetarget fuel injection amount acquired from the map shown in FIG. 2(A),“Kq” is the correction value for the target fuel injection amountcorrection calculated according to the formula 6 and “Kga” is thecorrection value for detected fresh air amount correction calculatedaccording to the formula 7.

AFe=(Ga×Kga)/(TQ×Kq)  (8)

Then, an air-fuel ratio difference rate Raf is calculated according tothe following formula 9. In the formula 9, “AFe” is the estimatedair-fuel ratio calculated according to the formula 8 and “AFd” is thedetected air-fuel ratio.

Raf=AFe/AFd  (9)

Then, a correction value for correcting the fuel injection amount forthe target EGR rate acquisition (hereinafter, this correction value willbe referred to as—instant correction value—) is calculated such that theair-fuel ratio difference rate Raf calculated according to the formula 9becomes “1” (i.e. the estimated air-fuel ratio corresponds to thedetected air-fuel ratio).

Then, the base correction value Kb is calculated according to thefollowing formula 10. In the formula 10, “Kpi” is the instant correctionvalue and “Kmap” is a learned correction value. The learned correctionvalue will be explained later in detail.

Kb=Kpi+Kmap+1  (10)

Next, an embodiment of the invention relating to the learned correctionvalue will be explained.

In one embodiment of the invention, as shown in FIG. 3, the learnedcorrection value Kmap is memorized in the electronic control unit 60 inthe form of a map as a function of the fuel injection amount Q and theengine speed N.

Then, the learned correction value Kmap corresponding to the fuelinjection amount Q and the engine speed N is acquired from the map shownin FIG. 3.

Then, this acquired learned correction value is used as the learnedcorrection value Kmap of the formula 10.

Further, the learned correction value is continually updated. That is,as explained above, in this embodiment, as shown in FIG. 3, the learnedcorrection value Kmap is memorized in the electronic control unit 60 inthe form of the map as a function of the fuel injection amount Q and theengine speed N.

In this regard, the initial value of the learned correction value Kmapis set as “0”.

Then, during the engine operation, when the instant correction value Kpiis calculated, the new learned correction value Kmap obtained by addingthis calculated instant correction value to the learned correction valueKmap of the map shown in FIG. 3 corresponding to the current fuelinjection amount Q (the current target fuel injection amount TQ is usedas this fuel injection amount Q) and the current engine speed N ismemorized in the map shown in FIG. 3 as the learned correction valuecorresponding to the current fuel injection amount Q and the currentengine speed N.

That is, during the engine operation, every the instant correction valueKpi is calculated, the learned correction value Kmap of the map shown inFIG. 3 corresponding to the current fuel injection amount Q and thecurrent engine speed N is updated by the instant correction value Kpi.

By controlling the EGR control valve as explained above, the estimatedEGR rate can be controlled to the target EGR rate while the estimatedair-fuel ratio can correspond to the detected air-fuel ratio. Next, thiswill be explained in detail.

As explained above, as far as the estimated EGR rate does not correspondto the target EGR rate, the EGR control valve opening degree iscontrolled such that the difference of the estimated EGR rate relativeto the target EGR rate becomes zero.

Therefore, even if the fuel injection amount used for acquiring thetarget EGR rate from the map shown in FIG. 2(C) is corrected in anyfashion by the correction value for the target fuel injection amountcorrection or even if the detected fresh air amount used for calculatingthe estimated EGR rate is corrected in any fashion by the correctionvalue for the detected fresh air amount correction, the estimated EGRrate is controlled conclusively to the target EGR rate.

Further, when the estimated air-fuel ratio is larger than the detectedair-fuel ratio, that is, when the estimated air-fuel ratio is leanerthan the detected air-fuel ratio, a value smaller than “0” is calculatedas the instant correction value.

Thereby, the base correction value calculated according to the formula10 is smaller than the last time calculated base correction value.

Then, in this case, the correction value for the target fuel injectionamount correction calculated by the formula 6 is smaller than the lastcorrection value for the target fuel injection amount correction and thecorrection value for the detected fresh air amount correction calculatedby the formula 7 is larger than the last correction value for thedetected fresh air amount correction.

Therefore, the fuel injection amount used for acquiring the target EGRrate is smaller than the last fuel injection amount. Thus, the targetEGR rate acquired from the map shown in FIG. 2(C) is larger than thelast time acquired target EGR rate.

Then, according to this, the EGR rate increases by the above-explainedcontrol of the EGR control valve and therefore, the detected air-fuelratio becomes smaller than the this time detected air-fuel ratio. Thatis, the detected air-fuel ratio approaches the this time calculatedestimated air-fuel ratio.

Further, the fuel injection amount used for calculating the estimatedair-fuel ratio is smaller than the last fuel injection amount while thedetected fresh air amount used for calculating the estimated air-fuelratio is larger than the last detected fresh air amount and therefore,the estimated air-fuel ratio becomes large. That is, the estimatedair-fuel ratio approaches the this time acquired detected air-fuelratio.

As explained above, the detected air-fuel ratio approaches the this timecalculated estimated air-fuel ratio while the estimated air-fuel ratioapproaches the this time acquired detected air-fuel ratio and therefore,the estimated air-fuel ratio corresponds to the detected air-fuel ratioconclusively.

On the other hand, when the estimated air-fuel ratio is smaller than thedetected air-fuel ratio, that is, when the estimated air-fuel ratio isricher than the detected air-fuel ratio, a value larger than “0” iscalculated as the instant correction value.

According to this, the base correction value calculated by the formula10 is larger than the last time calculated base correction value.

Then, in this case, the correction value for the target fuel injectionamount correction calculated by the formula 6 is larger than the lastcorrection value for the target fuel injection amount correction and thecorrection value for the detected fresh air amount correction calculatedby the formula 7 is smaller than the last correction value for thedetected fresh air amount correction.

Therefore, the fuel injection amount used for acquiring the target EGRrate is larger than the last fuel injection amount. Thus, the target EGRrate acquired from the map shown in FIG. 2(C) is smaller than the lasttime acquired target EGR rate.

Then, according to this, the EGR rate decreases by the above-explainedcontrol of the EGR control valve and therefore, the detected air-fuelratio becomes larger than the this time detected air-fuel ratio. Thatis, the detected air-fuel ratio approaches the this time calculatedestimated air-fuel ratio.

Further, the fuel injection amount used for calculating the estimatedair-fuel ratio is larger than the last fuel injection amount while thedetected fresh air amount used for calculating the estimated air-fuelratio is smaller than the last detected fresh air amount and therefore,the estimated air-fuel ratio becomes small. That is, the estimatedair-fuel ratio approaches the this time acquired detected air-fuelratio.

As explained above, the detected air-fuel ratio approaches the this timecalculated estimated air-fuel ratio while the estimated air-fuel ratioapproaches the this time acquired detected air-fuel ratio and therefore,the estimated air-fuel ratio corresponds to the detected air-fuel ratioconclusively.

When the estimated air-fuel ratio corresponds to the detected air-fuelratio, “0” is calculated as the instant correction value. According tothis, the base correction value calculated by the formula 10 is equal tothe last time calculated base correction value.

Then, in this case, the correction value for the target fuel injectionamount correction calculated by the formula 6 is equal to the lastcorrection value for the target fuel injection amount correction and thecorrection value for the detected fresh air amount correction calculatedby the formula 7 is equal to the correction value for the detected freshair amount correction.

Therefore, the fuel injection amount used for acquiring the target EGRrate is equal to the last fuel injection amount. Thus, the target EGRrate acquired from the map shown in FIG. 2(C) is equal to the last timeacquired target EGR rate. Thus, the detected air-fuel ratio does notchange. That is, the detected air-fuel ratio has corresponded to thethis time calculated estimated air-fuel ratio.

Further, the fuel injection amount used for calculating the estimatedair-fuel ratio is equal to the last fuel injection amount while thedetected fresh air amount used for calculating the estimated air-fuelratio is equal to the last detected fresh air amount and therefore, theestimated air-fuel ratio is equal to the this time estimated air-fuelratio. That is, the estimated air-fuel ratio has corresponded to thethis time acquired detected air-fuel ratio.

Thus, the condition that the estimated air-fuel ratio corresponds to thedetected air-fuel ratio is maintained.

As explained above, the change of the target EGR rate by correcting thefuel injection amount used for acquiring the target EGR rate dependingon the difference of the estimated air-fuel ratio relative to the targetair-fuel ratio has an advantage that the exhaust emission decreases.Next, this will be explained.

In the case that the estimated air-fuel ratio is larger than thedetected air-fuel ratio, that is, in the case that the estimatedair-fuel ratio is leaner than the detected air-fuel ratio, assuming thatthe upstream oxygen concentration sensor has no error, there is apossibility that the target fuel injection amount is smaller than theactual fuel injection amount.

In other words, there is a possibility that the actual fuel injectionamount is larger than the target fuel injection amount.

In this regard, the target EGR rate memorized in the map shown in FIG.2(C) is set as the EGR rate which can decrease the exhaust emissiondepending on the fuel injection amount. That is, if the target EGR ratesuitable for the actual fuel injection amount is not acquired from themap shown in FIG. 2(C), the exhaust emission decreases.

Therefore, there is a possibility that the actual fuel injection amountlarger than the target fuel injection amount and therefore, in order toimprove the exhaust emission, the target EGR rate corresponding to thelarge fuel injection amount should be acquired from the map shown inFIG. 2(C).

According to the above-explained embodiment, in the case that theestimated air-fuel ratio is larger than the detected air-fuel ratio,that is, in the case that there is a possibility that the actual fuelinjection amount is larger than the target fuel injection amount, thetarget fuel injection amount is maintained while the fuel injectionamount used for acquiring the target EGR rate from the map shown in FIG.2(C) is increased and therefore, as a result, the target EGR rate whichimproves the exhaust emission is acquired from the map shown in FIG.2(C) by the current actual fuel injection amount.

Similarly, in the case that the estimated air-fuel ratio is smaller thanthe detected air-fuel ratio, that is, in the case that the estimatedair-fuel ratio is richer than the detected air-fuel ratio, assuming thatthe upstream oxygen concentration sensor has no error, there is apossibility that the target fuel injection amount is larger than theactual fuel injection amount.

In other words, there is a possibility that the actual fuel injectionamount is smaller than the target fuel injection amount.

As explained above, the target EGR rate memorized in the map shown inFIG. 2(C) is set as the EGR rate which can improve the exhaust emissiondepending on the fuel injection amount.

That is, if the target EGR rate suitable for the actual fuel injectionamount is not acquired from the map shown in FIG. 2(C), the exhaustemission decreases.

Therefore, there is a possibility that the actual fuel injection amountis smaller than the target fuel injection amount and therefore, in orderto improve the exhaust emission, the target EGR rate corresponding tothe small fuel injection amount should be acquired from the map shown inFIG. 2(C).

According to the above-explained embodiment, in the case that theestimated air-fuel ratio is smaller than the detected air-fuel ratio,that is, in the case that there is a possibility that the actual fuelinjection amount is smaller than the target fuel injection amount, thetarget fuel injection amount is maintained while the fuel injectionamount used for acquiring the target EGR rate from the map shown in FIG.2(C) is decreased and therefore, as a result, the target EGR rate whichimproves the exhaust emission is acquired from the map shown in FIG.2(C) by the current actual fuel injection amount.

In the case that the base correction value is divided into thecorrection values for the target fuel injection amount correction andthe detected fresh air amount correction by using the distributioncoefficient as explained above, when the EGR control valve is controlledas explained above such that the estimated EGR rate is controlled to thetarget EGR rate and the estimated air-fuel ratio corresponds to thedetected air-fuel ratio, this can be accomplished for a short time.

Therefore, a high effect (for example, an effect to improve the exhaustemission) can be obtained from the above-explained control of the EGRcontrol valve.

That is, when the difference of the estimated air-fuel ratio relative tothe detected air-fuel ratio (in the above-explained embodiment, the basecorrection value) is divided into the correction values for the targetfuel injection amount correction and the detected fresh air amountcorrection by using the distribution coefficient, the correction valuefor the target fuel injection amount correction substantially representsthe fuel injection difference of the fuel injector and the correctionvalue for the detected fresh air amount correction substantiallyrepresents the fresh air amount detection difference of the air flowmeter.

In this regard, when the value obtained by dividing the estimatedair-fuel ratio by the detected air-fuel ratio is referred to as “airfuel ratio”, the value obtained by dividing the fresh air amountdetection difference by the fuel injection difference, that is, thevalue obtained by dividing the correction value for the detected freshair amount correction by the correction value for the target fuelinjection amount is equivalent to the air-fuel-ratio.

Then, from the study by the inventor of this application, when the valueobtained by dividing the correction value for the detected fresh airamount correction by the correction value for the target fuel injectionamount correction is equal to the air-fuel-ratio, it has been found thatit can be accomplished for a short time that the estimated EGR rate iscontrolled to the target EGR rate while the estimated air-fuel ratiocorresponds to the detected air-fuel ratio by controlling the EGRcontrol valve.

According to the above-explained embodiment, the value obtained bydividing the correction value for the detected fresh air amountcorrection by the correction value for the target fuel injection amountcorrection is equal to the air-fuel-ratio and therefore, it can beaccomplished for a short time that the estimated EGR rate is controlledto the target EGR rate while the estimated air-fuel ratio corresponds tothe detected air-fuel ratio by controlling the EGR control valve andfurthermore, the exhaust emission discharged from the combustion chambercan be improved.

Next, an example of a routine for performing the control of the fuelinjector will be explained. The example of this routine is shown in FIG.4. The routine shown in FIG. 4 is performed every a predetermined timehas elapsed.

When the routine shown in FIG. 4 starts, first, at the step 10, theaccelerator pedal opening degree Dac is acquired.

Next, at the step 11, the target fuel injection amount TQ is acquiredfrom the map shown in FIG. 2(A) on the basis of the accelerator pedalopening degree Dac acquired at the step 10.

Next, at the step 12, a fuel injector opening time TO for injecting thefuel having the target fuel injection amount TQ acquired at the step 11from the fuel injector is calculated.

Next, at the step 13, a command for opening the fuel injector by thefuel injector opening time TO calculated at the step 12 (hereinafter,this command will be referred to as—fuel injection command—) is outputto the fuel injector and then, the routine is terminated.

Next, an example of a routine for performing the control of the throttlevalve will be explained. The example of this routine is shown in FIG. 5.The routine shown in FIG. 5 is performed every a predetermined time haselapsed.

When the routine shown in FIG. 5 starts, first, at the step 20, theaccelerator pedal opening degree Dac and the engine speed are acquired.

Next, at the step 21, the target fuel injection amount TQ is acquired asthe fuel injection amount Q from the map shown in FIG. 2(A) on the basisof the accelerator pedal opening degree Dac acquired at the step 20.

Next, at the step 22, the target throttle valve opening degree TDth isacquired from the map shown in FIG. 2(B) on the basis of the fuelinjection amount Q acquired at the step 21 and the engine speed N.

Next, at the step 23, a command for accomplishing the target throttlevalve opening degree TD acquired at the step 22 is output to thethrottle valve and then, the routine is terminated.

Next, an example of a routine for performing the control of the EGRcontrol valve will be explained. The example of this routine is shown inFIG. 6. The routine shown in FIG. 6 is performed every a predeterminedtime has elapsed.

When the routine shown in FIG. 6 starts, first, at the step 30, theaccelerator pedal opening degree Dac, the engine speed N, the intakepressure Pim, the detected fresh air amount Ga and the correction valuesKq and Kga for the target fuel injection amount correction and thedetected fresh air amount correction.

Next, at the step 31, the target fuel injection amount TO is acquiredfrom the map shown in FIG. 2(A) on the basis of the accelerator pedalopening degree Dac acquired at the step 30.

Next, at the step 32, the fuel injection amount Q for the target EGRrate acquisition is calculated by applying the target fuel injectionamount TQ acquired at the step 31 and the correction value Kq for thetarget fuel injection amount correction acquired at the step 30 to theformula 4.

Next, at the step 33, the target EGR rate TRegr is acquired from the mapshown in FIG. 2(C) on the basis of the fuel injection amount Qcalculated at the step 32 and the engine speed N acquired at the step30.

Next, at the step 34, the in-cylinder intake gas amount Gc is calculatedby applying the intake pressure Pim and the engine speed N acquired atthe step 30 to the formula 3.

Next, at the step 35, the estimated EGR rate RegrE is calculated byapplying the in-cylinder intake gas amount Gc calculated at the step 34,the detected fresh air amount Ga and the correction value Kga for thedetected fresh air amount correction acquired at the step 30 to theformula 1.

Next, at the step 36, the EGR rate difference A Regr is calculated byapplying the target EGR rate TRegr calculated at the step 33 and theestimated EGR rate RegrE calculated at the step 35 to the formula 2.

Next, at the step 37, a command for controlling the EGR control valveopening degree is output to the EGR control valve such that the EGR ratedifference A Regr calculated at the step 36 becomes zero and then, theroutine is terminated.

Next, an example of a routine for performing the calculation of thecorrection values for the target fuel injection amount correction andthe detected fresh air amount correction and the update of the learnedcorrection value. This routine is shown in FIG. 7. The routine shown inFIG. 7 is performed every a predetermined time has elapsed.

When the routine shown in FIG. 7 starts, first, at the step 100, thedetected air-fuel ratio AFd, the detected fresh air amount Ga, theengine speed N, the accelerator pedal opening degree Dac, the correctionvalue Kq for the target fuel injection amount correction and thedistribution coefficient Kd are acquired.

Next, at the step 101, the target fuel injection amount TQ is acquiredfrom the map shown in FIG. 2(A) on the basis of the accelerator pedalopening degree Dac acquired at the step 100.

Next, at the step 102, the learned correction value Kmap is acquiredfrom the map shown in FIG. 3 on the basis of the target fuel injectionamount TQ acquired at the step 101 and the engine speed N acquired atthe step 100.

Next, at the step 103, the estimated air-fuel ratio AFe is calculated byapplying the target fuel injection amount TQ acquired at the step 101,the detected fresh air amount Ga and the correction value Kq for thetarget fuel injection amount acquired at the step 100 to the formula 8.

Next, at the step 104, the air-fuel ratio difference rate Raf iscalculated by applying the estimated air-fuel ratio AFe calculated atthe step 103 and the detected air-fuel ratio AFd acquired at the step100.

Next, at the step 105, a correction value for correcting the fuelinjection amount for the target EGR rate acquisition is calculated asthe instant correction value Kpi such that the air-fuel ratio differencerate Raf calculated at the step 104 becomes “1”.

Next, at the step 106, the base correction value Kb is calculated byapplying the instant correction value Kpi calculated at the step 105 andthe learned correction value Kmap acquired at the step 102 to theformula 10.

Next, at the step 107, the correction value Kq for the target fuelinjection amount correction is calculated by applying the basecorrection value Kb calculated at the step 106 and the distributioncoefficient Kd acquired at the step 100 to the formula 6 while thecorrection value Kga for the detected fresh air amount correction iscalculated by applying the base correction value Kb calculated at thestep 106 and the distribution coefficient Kd acquired at the step 100 tothe formula 7.

Next, at the step 108, a value obtained by adding the instant correctionvalue Kpi calculated at the step 105 to the learned correction valueKmap acquired at the step 102 is updated as a new learned correctionvalue Kmap and then, the routine is terminated.

Next, an embodiment of the invention relating to the setting of thedistribution coefficient Kd will be explained.

In the following explanation, “fuel injector tolerance” is a drawingstolerance relating to the accuracy of the fuel injection amount from thefuel injector relative to the fuel injection command, “air flow metertolerance” is a drawings tolerance relating to the detection accuracy ofthe fresh air amount by the air flow meter, “oxygen concentration sensortolerance” is a drawings tolerance relating to the detection accuracy ofthe oxygen concentration by the upstream oxygen concentration sensor,“NOx production amount” is an amount of the NOx (nitrogen oxide)produced in the combustion chamber per unit running distance and“accumulated running distance” is an accumulated running distance of avehicle which the engine of the invention is mounted.

In one embodiment of the invention (hereinafter, this embodiment will bereferred to as—first embodiment relating to the distribution coefficientsetting—), first, the engine which the fuel injectors having no fuelinjection amount difference, the air flow meter having no detected freshair amount difference and the upstream oxygen concentration sensorhaving no detected oxygen concentration difference are mounted isoperated at a predetermined operation mode under the condition where thebase correction value Kb is maintained “1” (i.e. the condition that thecorrection values for the target fuel injection amount correction andthe detected fresh air amount correction and substantially, thecondition that the target fuel injection amount and detected fresh airamount are not corrected) and then, the current NOx production amount(hereinafter, this NOx production amount will be referred to as—base NOxproduction amount—) is acquired.

Then, in this embodiment, a first distribution coefficient map isprepared as follows.

That is, first, the engine which new fuel injectors having the fuelinjection amount difference, the air flow meter having no detected freshair amount difference and the upstream oxygen concentration sensorhaving no detected oxygen concentration difference are mounted isoperated at the above-mentioned predetermined operation mode under thecondition where the calculation of the base correction value on thebasis of the air-fuel ratio difference ratio is performed and thedistribution coefficient Kd is fixed to “0”.

Then, during this engine operation, the data of the NOx productionamounts (hereinafter, this NOx production amount will be referred toas—first NOx production amount—) are acquired.

Then, a plurality of NOx index values (i.e. index values relating to theNOx produced in the combustion chamber and hereinafter, this NOx indexvalue will be referred to as—first NOx index value—) ID1 are calculatedby applying the data of the first NOx production amounts to thefollowing formula 11 one by one.

In the following formula 11, “NOXb” is a base NOx production amount and“NOX1) is a first NOx production amount.

ID1=NOX1/NOXb−1  (11)

Further, the engine which new fuel injectors having the fuel injectionamount difference, the air flow meter having no detected fresh airamount difference and the upstream oxygen concentration sensor having nodetected oxygen concentration difference are mounted is operated at theabove-mentioned operation mode under the condition where the calculationof the base correction value on the basis of the air-fuel ratiodifference ratio is performed and the distribution coefficient Kd isfixed to “1”.

Then, during this engine operation, the date of the NOx productionamounts (hereinafter, this NOx production amount will be referred toas—second NOx production amount—) are acquired.

Then, a plurality of NOx index values (hereinafter, this NOx index valuewill be referred to as—second NOx index value—) 102 are calculated byapplying the data of the second NOx production amounts to the followingformula 12 one by one.

In the following formula 12, “NOXb” is the base NOx production amountand “NOX2” is a second NOx production amount.

ID2=NOX2/NOXb−1  (12)

Further, the engine which the fuel injectors having no fuel injectionamount difference, new air flow meter having the detected fresh airamount difference and the upstream oxygen concentration sensor having nodetected oxygen concentration difference are mounted is operated at theabove-mentioned operation mode under the condition where the calculationof the base correction value on the basis of the air-fuel ratiodifference ratio is performed and the distribution coefficient Kd isfixed to “0”.

Then, during this engine operation, the data of the NOx productionamounts (hereinafter, this NOx production amount will be referred toas—third NOx production amount—) are acquired.

Then, a plurality of NOx index values (hereinafter, this NOx index valuewill be referred to as—third NOx index value—) ID3 are calculated byapplying the data of the third NOx production amounts to the followingformula 13 one by one.

In the following formula 13, “NOXb” is the base NOx production amountand “NOX3” is a third NOx production amount.

ID3=NOX3/NOXb−1  (13)

Further, the engine which the fuel injectors having no fuel injectionamount difference, new air flow meter having the detected fresh airamount difference and the upstream oxygen concentration sensor having nodetected oxygen concentration difference are mounted is operated at theabove-mentioned operation mode under the condition where the calculationof the base correction value on the basis of the air-fuel ratiodifference ratio is performed and the distribution coefficient Kd isfixed to “1”.

Then, during this engine operation, the date of the NOx productionamounts (hereinafter, this NOx production amount will be referred toas—fourth NOx production amount—) are acquired.

Then, a plurality of NOx index values (hereinafter, this NOx index valuewill be referred to as—fourth NOx index value—) ID4 are calculated byapplying the data of the fourth NOx production amounts to the followingformula 14 one by one.

In the following formula 14, “NOXb” is the base NOx production amountand “NOX4” is a fourth NOx production amount.

ID4=NOX4/NOXb−1  (14)

Further, the engine which the fuel injectors having no fuel injectionamount difference, the air flow meter having no detected fresh airamount difference and new upstream oxygen concentration sensor havingthe detected oxygen concentration difference are mounted is operated atthe above-mentioned operation mode under the condition where thecalculation of the base correction value on the basis of the air-fuelratio difference ratio is performed and the distribution coefficient Kdis fixed to “0”.

Then, during this engine operation, the data of the NOx productionamounts (hereinafter, this NOx production amount will be referred toas—fifth NOx production amount—) are acquired.

Then, a plurality of NOx index values (hereinafter, this NOx index valuewill be referred to as—fifth NOx index value—) ID5 are calculated byapplying the data of the fifth NOx production amounts to the followingformula 15 one by one.

In the following formula 15, “NOXb” is the base NOx production amountand “NOX5” is a fifth NOx production amount.

ID5=NOX5/NOXb−1  (15)

Further, the engine which the fuel injectors having no fuel injectionamount difference, the air flow meter having no detected fresh airamount difference and new upstream oxygen concentration sensor havingthe detected oxygen concentration difference are mounted is operated atthe above-mentioned operation mode under the condition where thecalculation of the base correction value on the basis of the air-fuelratio difference ratio is performed and the distribution coefficient Kdis fixed to “1”.

Then, during this engine operation, the data of NOx production amounts(hereinafter, this NOx production amount will be referred to as—sixthNOx production amount—) are acquired.

Then, a plurality of NOx index values (hereinafter, this NOx index valuewill be referred to as—sixth NOx index value—) ID6 are calculated byapplying the data of the sixth NOx production amounts to the followingformula 16 one by one.

In the following formula 16, “NOXb” is the base NOx production amountand “NOX6” is a sixth NOx production amount.

ID6=NOX6/NOXb−1  (16)

Then, the first to sixth NOx index values which have the samecombination of the target fuel injection amount and the engine speedrelating thereto are selected from the thus calculated first to sixthNOx index values ID1 to ID6 and then, as shown in FIG. 8, in thecoordinate having the abscissa of the distribution coefficient Kd andthe ordinate of the NOx index value ID, the first NOx index value ID1 isplotted on the line of “0” of the distribution coefficient Kd (this plotpoint is shown by the reference symbol ID1 in FIG. 8), the second NOxindex value ID2 is plotted on the line of “1” of the distributioncoefficient Kd (this plot point is shown by the reference symbol ID2 inFIG. 8), the third NOx index value ID3 is plotted on the line of “0” ofthe distribution coefficient Kd (this plot point is shown by thereference symbol ID3 in FIG. 8), the fourth NOx index value ID4 isplotted on the line of “1” of the distribution coefficient Kd (this plotpoint is shown by the reference symbol ID4 in FIG. 8), the fifth NOxindex value ID5 is plotted on the line of “0” of the distributioncoefficient Kd (this plot point is shown by the reference symbol ID5 inFIG. 8) and the sixth NOx index value ID6 is plotted on the line of “1”of the distribution coefficient Kd (this plot point is shown by thereference symbol ID6 in FIG. 8).

Then, the plot points ID1 and ID2 are connected by a straight line (thisstraight line is shown by the reference symbol Li), he plot points ID3and ID4 are connected by a straight line (this straight line is shown bythe reference symbol La and the plot points ID5 and ID6 are connected bya straight line (this straight line is shown by the reference symbolLo).

Then, from the distribution coefficients Kd1 and Kd2 corresponding tothe intersection points IS1 and IS2 respectively of the straight linesLi and La, the distribution coefficient where the value obtained byadding together the NOx index values on each straight lines Li, La andLo corresponding to the distribution coefficients Kd1 and Kd2respectively (in FIG. 8, the distribution coefficient Kd2) is acquiredas the distribution coefficient to be employed as the distributioncoefficient constituting the first distribution coefficient map.

Then, a plurality of the distribution coefficients to be employed as thedistribution coefficients constituting the first distributioncoefficient map are acquired by performing the above-explained processrepeatedly corresponding to each combination of the target fuelinjection amount and the engine speed relating to the NOx index valueand then, as shown in FIG. 9(A), the first distribution map used foracquiring the distribution coefficient Kd on the basis of the targetfuel injection amount TQ and engine speed N is prepared on the basis ofthe acquired distribution coefficients.

Further, in this embodiment, the second distribution coefficient map isprepared as follows.

That is, first, the engine comprising the fuel injectors used for acertain time and having an error, the air flow meter having no error andthe upstream oxygen concentration sensor having no error is operated atthe above-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “0” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—firstNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID1 are calculated by applyingthe data of the first NOx production amounts to the formula 11 one byone (hereinafter, this NOx index value will be referred to as—first NOxindex value—).

Further, the engine comprising the fuel injectors used for a certaintime and having an error, the air flow meter having no error and theupstream oxygen concentration sensor having no error is operated at theabove-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “1” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—secondNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID2 are calculated by applyingthe data of the second NOx production amounts to the formula 12 one byone (hereinafter, this NOx index value will be referred to as—second NOxindex value—).

Further, the engine comprising the fuel injectors having no error, theair flow meter used for a certain time and having an error and theupstream oxygen concentration sensor having no error is operated at theabove-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “0” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—thirdNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID3 are calculated by applyingthe data of the third NOx production amounts to the formula 13 one byone (hereinafter, this NOx index value will be referred to as—third NOxindex value—).

Further, the engine comprising the fuel injectors having no error, theair flow meter used for a certain time and having an error and theupstream oxygen concentration sensor having no error is operated at theabove-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “1” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—fourthNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID4 are calculated by applyingthe data of the fourth NOx production amounts to the formula 14 one byone (hereinafter, this NOx index value will be referred to as—fourth NOxindex value—).

Further, the engine comprising the fuel injectors having no error, theair flow meter having no error and the upstream oxygen concentrationsensor used for a certain time and having an error is operated at theabove-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “0” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—fifthNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID5 are calculated by applyingthe data of the third NOx production amounts to the formula 15 one byone (hereinafter, this NOx index value will be referred to as—fifth NOxindex value—).

Further, the engine comprising the fuel injectors having no error, theair flow meter having no error and the upstream oxygen concentrationsensor used for a certain time and having an error is operated at theabove-mentioned operation mode under the condition where thedistribution coefficient Kd is maintained “1” and the calculation of thebase correction value on the basis of the air-fuel ratio differenceratio is performed.

Then, during the engine operation, the data of the NOx production amount(hereinafter, this NOx production amount will be referred to as—sixthNOx production amount—) are acquired.

Then, a plurality of the NOx index values ID6 are calculated by applyingthe data of the third NOx production amounts to the formula 16 one byone (hereinafter, this NOx index value will be referred to as—six NOxindex value—).

Then, the first to sixth NOx index values corresponding to the samecombination of the target fuel injection amount and the engine speed arefound from the first to sixth NOx index values ID1 to ID6 calculated asexplained above, a plurality of distribution coefficients to be employedas distribution coefficients for constituting a second distributioncoefficient map are acquired by the same process as that explainedrelating to the preparation of the first distribution coefficient map,and the second distribution coefficient map used for acquiring thedistribution coefficient Kd from the target fuel injection amount TQ andthe engine speed N is prepared on the basis of the acquired distributioncoefficients as shown in FIG. 9(B).

Regarding the preparation of the second distribution coefficient map,the “fuel injector used for a certain time” is a fuel injector of anengine when the vehicle having the engine having new fuel injectorsmounted has run for a predetermined distance, the “air flow meter usedfor a certain time” is an air flow meter of an engine when the vehiclehaving the engine having new air flow meter mounted has run for apredetermined distance, and the “upstream oxygen concentration sensorused for a certain time” is an upstream oxygen concentration sensor ofan engine when the vehicle having the engine having new upstream oxygenconcentration sensor mounted has run for a predetermined distance.

Then, during the engine operation, when the total sum running distanceis shorter than a base total sum running distance (i.e. theabove-mentioned predetermined distance), the distribution coefficientacquired from the first distribution coefficient map on the basis of thecurrent target fuel injection amount and the current engine speed is setas the distribution coefficient used for the actual engine control(hereinafter, this distribution coefficient will be also referred toas—distribution coefficient for the engine control—).

On the other hand, during the engine operation, when the total sumrunning distance is equal to or larger than the base total sum runningdistance, the distribution coefficient acquired from the seconddistribution coefficient on the basis of the current target fuelinjection amount and the current engine speed is set as the distributioncoefficient for the engine speed.

According to the above-explained setting of the distributioncoefficient, the distribution coefficient is set in consideration of thefuel injector tolerance, the air flow meter tolerance and the oxygenconcentration sensor tolerance.

Thus, even when the fuel injector has a fuel injection difference in therange of the drawings tolerance, or the air flow meter has a fresh airamount detection difference in the range of the drawings tolerance, orthe upstream oxygen concentration sensor has an error in the range ofthe drawings tolerance, the amount of NOx discharged from the combustionchamber can be decreased and therefore, the distribution coefficientwhich can decrease the exhaust emission discharged from the combustionchamber is set.

Next, another embodiment of the invention relating to the setting of thedistribution coefficient Kd will be explained.

In this another embodiment of the invention (hereinafter, thisembodiment will be referred to as—second embodiment relating to thedistribution coefficient setting—), first, the engine equipped with thefuel injector having no fuel injection difference, the air flow meterhaving no fresh air amount detection difference and the upstream oxygenconcentration sensor having no error is operated at a predeterminedoperation mode in the condition that the base correction value Kb ismaintained at the constant value “1” (i.e. the correction values for thetarget fuel injection amount correction and the detected fresh airamount correction are “1”, respectively and therefore, the target fuelinjection amount and the detected fresh air amount are not correctedsubstantially) and then, under this condition, the NOx productionamounts are previously acquired (hereinafter, this NOx production amountwill be referred to as—base NOx production amount—).

Then, during the engine operation, the currently-used distributioncoefficient Kd is used as the base distribution coefficient.

Then, the engine is operated in the condition that this basedistribution coefficient is used as the provisional distributioncoefficient and then, under this condition, the NOx production amountsare detected and thereafter, the index values relating to NOx producedin the combustion chamber IDb are calculated by applying the detectedNOx production amounts to the following formula 17 (hereinafter, thisindex value will be referred to as—base NOx index value—).

In the formula 17, “NOXdb” is the detected NOx production amount and“NOXb” is the base NOx production amount.

IDb=NOXdb/NOXb−1  (17)

Next, the engine is operated in the condition that the value smallerthan the currently-used distribution coefficient by the predeterminedvalue (this value is larger than zero) is used as the provisionaldistribution coefficient (i.e. the value smaller than the basedistribution coefficient by the predetermined value) and then, the NOxproduction amounts are detected and thereafter, the index values IDsrelating to NOx produced in the combustion chamber are calculated byapplying the detected NOx production amounts to the following formula 18(hereinafter, this index value will be referred to as—decrease-side NOxindex value—).

In the formula 18, “NOXds” is the detected NOx production amount and“NOXb” is the base NOx production amount.

IDs=NOXds/NOXb−1  (18)

Next, the engine is operated in the condition that the value larger thanthe currently-used distribution coefficient by the predetermined value(this value is larger than zero) is used as the provisional distributioncoefficient and then, the NOx production amounts are detected andthereafter, the index values IDl relating to NOx produced in thecombustion chamber are calculated by applying the detected NOxproduction amounts to the following formula 19 (hereinafter, this indexvalue will be referred to as—increase-side NOx index value—).

In the formula 19, “NOXdl” is the detected NOx production amount and“NOXb” is the base NOx production amount.

IDl=NOXdl/NOXb−1  (19)

Then, the calculated NOx index values are compared with each other andthen, it is judged which value is the smallest.

In this regard, when it is judged that the base NOx index IDb calculatedby the formula 17 is the smallest, the base distribution coefficientused at this time is set to the distribution coefficient and then, thesetting of the distribution coefficient is terminated.

That is, in this case, the currently-used distribution coefficientitself is used as the distribution coefficient.

On the other hand, when it is judged that the decrease-side NOx indexvalue IDs calculated by the formula 18 is the smallest, the calculationof the NOx index values IDb, IDs and IDl according to the formulas 17 to19 and the comparison thereof are performed in the condition that thevalue smaller than the base distribution coefficient used at this timeby the predetermined value (this value is larger than zero) is sed as anew base distribution coefficient.

That is, the value smaller than the base distribution coefficient usedat this time by the predetermined value is used as a new basedistribution coefficient, the engine is operated in the condition thatthis new base distribution coefficient is used as the provisionaldistribution coefficient and then, the NOx production amount is detectedand thereafter, the base NOx index value IDb is calculated by applyingthe detected NOx production amount NOXdb to the formula 17, and next,the engine is operated in the condition that the value smaller than thenew base distribution coefficient by the predetermined value is used asthe provisional distribution coefficient and then, the NOx productionamount is detected and thereafter, the decrease-side NOx index value IDsis calculated by applying the detected NOx production amount NOXds tothe formula 18, and next, the operation is operated in the conditionthat the value larger than the new base distribution coefficient by thepredetermined value is used as the provisional distribution coefficientand then, the NOx production amount is detected and thereafter, theincrease-side NOx index value IDl is calculated by applying the detectedNOx production amount NOXdl to the formula 19.

Then, the calculated NOx index values are compared with each other andit is judged which NOx index value is the smallest.

In this regard, when it is judged that the base NOx index value IDbcalculated by the formula 18 is the smallest, the base distributioncoefficient used at this time is set to the distribution coefficient andon the other hand, when it is judged that the decrease-side NOx indexvalue IDs calculated by the formula 17 is the smallest, theabove-explained engine operation, NOx production amount detection, NOxindex value calculation and NOx index value comparison are performed inthe condition that the value smaller than the base distributioncoefficient used at this time by the predetermined value is used as anew base distribution coefficient and this process is performedrepeatedly until it is judged that the base NOx index value IDbcalculated by the formula 18 is the smallest.

On the other hand, when it is judged that the increase-side NOx indexvalue IDl calculated by the formula 19 is the smallest, the calculationof the NOx index values IDb, IDs and IDl according to the formulas 17 to19 and the comparison of these NOx index values are performed in thecondition that the value larger than the base distribution coefficientused at this time by the predetermined value (this value is larger thanzero) is used as a new base distribution coefficient.

That is, the value larger than the base distribution coefficient used atthis time by the predetermined value is used as a new base distributioncoefficient, the engine is operated in the condition that this new basedistribution coefficient is used as the provisional distributioncoefficient and then, the NOx production amount is detected andthereafter, the base NOx index value IDb is calculated by applying thedetected NOx production amount NOXdb to the formula 17 and next, theengine is operated in the condition that the value smaller than the newbase distribution coefficient by the predetermined value is used as theprovisional distribution coefficient and then, the NOx production amountis detected and thereafter, the decrease-side NOx index value IDs iscalculated by applying the detected NOx production amount NOXds to theformula 18 and next, the engine is operated in the condition that thevalue larger than the new base distribution coefficient by thepredetermined value is used as the provisional distribution coefficientand then, the NOx production amount is detected and thereafter, theincrease-side NOx index value IDl is calculated by applying the detectedNOx production amount NOXdl to the formula 19.

Then, the calculated NOx index values are compared with each other andthen, it is judged which NOx index value is the smallest.

In this regard, when it is judged that the base NOx index value IDbcalculated by the formula 18 is the smallest, the base distributioncoefficient used at this time is set to the distribution coefficient andon the other hand, when it is judged that the increase-side NOx indexvalue IDl calculated by the formula 19 is the smallest, theabove-explained engine operation, NOx production amount detection, NOxindex value calculation and NOx index value comparison are performed inthe condition that the value larger than the base distributioncoefficient used at this time by the predetermined value is used as anew base distribution coefficient and this process is performedrepeatedly until it is judged that the base NOx index value IDbcalculated by the formula 17 is the smallest.

Of course, when it is judged that the decrease-side NOx index value IDscalculated by the formula 18 is the smallest, the above-explained engineoperation, NOx production amount detection, NOx index value calculationand NOx index value comparison are performed in the condition that thevalue smaller than the base distribution coefficient used at this timeby the predetermined value is used as a new base distributioncoefficient and thereafter, when it is judged that the increase-side NOxindex value IDl calculated by the formula 19 is the smallest, theabove-explained engine operation, NOx production amount detection, NOxindex value calculation and NOx index value comparison are performed inthe condition that the base distribution coefficient is increased by thepredetermined value.

On the other hand, when it is judged that the maximum NOx index valueIDl calculated by the formula 19 is the smallest, the above-explainedengine operation, NOx production amount detection, NOx index valuecalculation and NOx index value comparison are performed in thecondition that the value larger than the base distribution coefficientused at this time by the predetermined value is used as a new basedistribution coefficient and thereafter, when it is judged that thedecrease-side NOx index value IDs calculated by the formula 18 is thesmallest, the above-explained engine operation, NOx production amountdetection, NOx index value calculation and NOx index value comparisonare performed in the condition that the base distribution coefficient isdecreased by the predetermined value.

According to the above-explained distribution coefficient setting, evenwhen the fuel injection difference occurs in the fuel injector or thisdifference changes due to the fuel injector deterioration or even whenthe fresh air amount detection difference occurs in the air flow meteror this difference changes due to the air flow meter deterioration oreven when the oxygen concentration detection difference occurs in theupstream oxygen concentration sensor or this difference changes due tothe upstream oxygen concentration sensor deterioration, a newdistribution coefficient is set in reflection of these differenceoccurrence or changes during the engine operation.

Thus, the NOx amount discharged from the combustion chamber can bedecreased and therefore, the distribution coefficient which can decreasethe exhaust emission discharged from the combustion chamber is set.

Next, an example of the routine for performing the setting of the secondembodiment will be explained. This routine is shown in FIG. 10. Theroutine shown in FIG. 10 is performed every a predetermined time haselapsed.

When the routine shown in FIG. 10 starts, first, at the step 200, thebase distribution coefficient Kdb is set as the provisional distributioncoefficient Kdp.

Next, at the step 201, the NOx production amount NOXdb is detected whenthe engine is operated using the provisional distribution coefficientKdp set at the step 200.

Next, at the step 202, the value smaller than the base distributioncoefficient Kdb by the predetermined value ΔK is set as the provisionaldistribution coefficient Kdp.

Next, at the step 203, the NOx production amount NOXds is detected whenthe engine is operated using the provisional distribution coefficientKdp set at the step 202.

Next, at the step 204, the value larger than the base distributioncoefficient Kdb by the predetermined value ΔK is set as the provisionaldistribution coefficient Kdp.

Next, at the step 205, the NOx production amount NOXdl is detected whenthe engine is operated using the provisional distribution coefficientKdp set at the step 204.

Next, at the step 206, the base NOx index value IDb is calculated byapplying the NOx production amount NOXdb detected at the step 201 to theformula 17 and then, the decrease-side NOx index value IDs is calculatedby applying the NOx production amount NOXds detected at the step 203 tothe formula 18 and then, the increase-side NOx index value IDl iscalculated by applying the NOx production amount NOXdl detected at thestep 205 to the formula 19.

Next, at the step 207, it is judged if the base NOx index value IDbcalculated at the step 206 is smaller than the decrease-side NOx indexvalue IDs calculated at the step 206 (IDb<IDs) and the increase-side NOxindex value Idl calculated at the step 206 (IDb<IDs).

In this regard, when it is judged that IDb<IDs and IDb<IDl, the routineproceeds to the step 208.

On the other hand, when it is judged that IDb≧IDs or IDb≧IDl, theroutine proceeds to the step 209.

When it is judged at the step 207 that IDb<IDs and IDb<IDl, that is, thebase NOx index value IDb is the smallest among the three NOx indexvalues IDb, IDs and IDl and then, the routine proceeds to the step 208,the base distribution coefficient Kdb set as the provisionaldistribution coefficient Kdp at the step 200 is set as the distributioncoefficient Kd and then, the routine is terminated.

On the other hand, when it is judged at the step 207 that IDb or IDbthat is, the base NOx index value IDb is the smallest among the threeNOx index values IDb, IDs and IDl and then, the routine proceeds to thestep 209, it is judged if the decrease-side NOx index value IDscalculated at the step 206 is smaller than the base NOx index value IDbcalculated at the step 206 (IDs<IDb) and the increase-side NOx indexvalue 101 calculated at the step 206 (IDs<IDl).

In this regard, when it is judged that IDs<IDb and IDs<IDl, the routineproceeds to the step 210.

On the other hand, when it is judged that IDs≧IDb or IDs≧IDl, theroutine proceeds to the step 211.

When it is judged at the step 209 that IDs<IDb and IDs<IDl, that is, thedecrease-side NOx index value IDs is the smallest among the three NOxindex values IDb, IDs and IDl and then, the routine proceeds to the step210, the value smaller than the base distribution coefficient Kdb set asthe provisional distribution coefficient Kdp at the step 200 by thepredetermined value ΔK is set as a new base distribution coefficient Kdband then, the routine returns to the step 200.

On the other hand, when it is judged at the step 209 that IDs≧IDb orIDs≧IDl, that is, the decrease-side NOx index value IDs is not thesmallest among the three NOx index values IDb, IDs and IDl and then, theroutine proceeds to the step 211, the value larger than the basedistribution coefficient Kdb set as the provisional coefficient Kdp atthe step 200 by the predetermined value ΔK is set as a new basedistribution coefficient and then, the routine returns to the step 200.

Next, the embodiment of the invention relating to the malfunctiondiagnosis of the fuel injector using the correction value for the targetfuel injection amount correction calculated as explained above will beexplained.

In one embodiment of the invention, when the accuracy of the fuelinjection amount by the fuel injector (hereinafter, this accuracy willbe referred to as—fuel injection amount accuracy—) is within theallowable range, the correction value Kq for the target fuel injectionamount correction calculated in the above-explained embodiment is withina certain constant range.

That is, when the correction value Kq for the target fuel injectionamount correction is not within a range corresponding to the allowablefuel injection amount accuracy range, the fuel injection amount accuracyis not within the allowable range and therefore, it may be judged thatthe malfunction occurs in the fuel injector.

Thus, the range of the correction value Kq for the target fuel injectionamount correction corresponding to the allowable fuel injection amountaccuracy range is previously obtained as an allowable correction valuerange by an experiment, etc. and when the correction value for thetarget fuel injection amount correction calculated during the engineoperation is not within the allowable correction amount range, it can bejudged that the malfunction occurs in the fuel injector.

In the above-explained fuel injector malfunction diagnosis, even whenthe fuel injection difference occurs in the fuel injection or thisdifferece changes due to the fuel injector deterioration or even whenthe fresh air amount detection difference occurs in the air flow meteror this differece changes due to the air flow meter deterioration oreven when the oxygen concentration detection difference occurs or thisdifference changes due to the upstream oxygen concentration sensordeterioration, the fuel injector malfunction diagnosis is performed onthe basis of the correction value for the target fuel injection amountcorrection calculated using the distribution coefficient in reflectionof the difference occurrences or changes.

Thus, the fuel injector malfunction can be diagnosed accurately.

Next, an example of a routine for performing the fuel injectormalfunction diagnosis of the above-explained embodiment will beexplained. This routine is shown in FIG. 11. The routine shown in FIG.11 is performed every a predetermined time has elapsed.

When the routine shown in FIG. 11 starts, first, at the step 300, thecorrection value Kq for the target fuel injection amount correction isacquired.

Next, at the step 301, it is judged if the correction value Kq acquiredat the step 300 is equal to or larger than the lower limit value Kqmimand is equal to or smaller than the upper limit value Kqmax(Kqmim≦Kq≦Kqmax).

When it is judged that Kqmim≦Kq≦Kqmax, the routine is terminateddirectly.

In this case, it is diagnosed that no malfunction occurs in the fuelinjector.

On the other hand, it is not judged that Kqmim≦Kq≦Kqmax, the routineproceeds to the step 302 where it is diagnosed that a malfunction occursin the fuel injector and then, the routine is terminated.

Next, an embodiment of the invention relating to the air flow metermalfunction diagnosis using the correction value for the detected freshair amount correction calculated as explained above will be explained.

In one embodiment of the invention, when the detection accuracy of thefresh air by the air flow meter (hereinafter, this accuracy will bereferred to as—fresh air amount detection accuracy—) is within theallowable range, the correction value Kga for the detected fresh airamount correction calculated in the above-explained embodiment is withina certain constant range.

That is, when the correction value Kga for the detected fresh air amountcorrection is not within the range corresponding to the allowable rangeof the fresh air amount detection accuracy, the fresh air amountdetection accuracy is not within the allowable range and it can bejudged that a malfunction occurs in the air flow meter.

Thus, the range of the correction value Kga for the detected fresh airamount correction corresponding to the allowable range of the fresh airamount detection accuracy is obtained previously by an experiment, etc.,and it may be diagnosed that a malfunction occurs in the air flow meterwhen the correction value for the detected fresh air amount correctioncalculated during the engine operation is not within the above-mentionedallowable correction value range.

In the above-explained air flow meter malfunction diagnosis, even whenthe fuel injection difference occurs in the fuel injector or thisdifference changes due to the fuel injector deterioration or when thefresh air amount detection difference occurs in the air flow meter orthis difference changes due to the air flow meter deterioration or whenthe oxygen concentration detection difference occurs in the upstreamoxygen concentration sensor or this difference changes due to theupstream oxygen concentration sensor deterioration, the air flow metermalfunction diagnosis is performed on the basis of the correction valuefor the detected fresh air amount correction calculated using thedistribution coefficient in reflection of these difference occurrencesor changes.

Thus, the air flow meter malfunction can be diagnosed accurately.

Next, an example of a routine for performing the air flow metermalfunction diagnosis of the above-explained embodiment will beexplained. This routine is shown in FIG. 12. The routine shown in FIG.12 is performed every a predetermined time has elapsed.

When the routine shown in FIG. 12 starts, first, at the step 400, thecorrection value Kga for the detected fresh air amount correction isacquired.

Next, at the step 401, it is judged if the correction value Kga acquiredat the step 400 is equal to or larger than the lower limit value Kgamimand is equal to or smaller than the upper limit value Kgamax(Kgamim≦Kga≦Kgamax).

When it is judged that Kgamim≦Kga≦Kgamax, the routine is terminateddirectly.

In this case, it is not diagnosed that a malfunction occurs in the airflow meter.

On the other hand, when it is not judged that Kgamim≦Kga≦Kgamax, theroutine proceeds to the step 402 where it is judged that a malfunctionoccurs in the air flow meter and then, the routine is terminated.

In the above-explained embodiment, the feedback control of the EGRcontrol valve opening degree on the basis of the EGR rate difference is,for example, a so-called PI control (i.e. a proportional integralcontrol).

Further, in the above-explained embodiment, the target fuel injectionamount correction by the correction value for the target fuel injectionamount correction may be performed independently of the engine operationcondition or this correction may be performed only when the engineoperation condition meets the operation condition suitable or necessaryto perform this correction.

Further, in the above-explained embodiment, the detected fresh airamount correction by the correction value for the detected fresh airamount correction may be performed independently of the engine operationcondition or this correction may be performed only when the engineoperation condition meets the operation condition suitable or necessaryto perform this correction.

Further, in the above-explained embodiment, the instant correction valueKpi used for calculating the base correction value Kb is, for example, acorrection value for correcting the fuel injection amount for the targetEGR rate acquisition so as to make the estimated air-fuel ratiocorrespond to the detected air-fuel ratio by controlling the fresh airamount by the proportional integral feedback control of the EGR rate.

Further, in the above-explained embodiment, the instant correction valuemay be reflected in the base correction value independently of theengine operation condition or only when the engine operation conditionmeets a defined operation condition.

In this regard, in order not to reflect the instant correction value tothe base correction value when the engine operation state does notsatisfy a particular state, for example, the base correction value iscalculated according to the formula 10 under the condition where theinstant correction value is “0”.

Further, the defined operation condition is, for example, a conditionthat the detected air-fuel ratio is not extremely rich or lean or acondition that the detected air-fuel ratio change is relatively small ora condition that the fuel injection amount change is relatively small ora condition that the intake pressure change is relatively small or acombination of at least two of these conditions.

Further, in the above-explained embodiment, the target fuel injectionamount correction by the correction value for the target fuel injectionamount correction or the detected fresh air amount correction by thecorrection value for the detected fresh air amount correction may beperformed independently of the engine operation condition or only whenthe engine operation condition meets a defined operation condition.

In this regard, in order not to perform these corrections when theengine operation state does not satisfy a particular state, for example,“1” is set to the base correction value.

Further, the defined operation condition is, for example, a conditionthat the engine speed is not extremely large or small or a conditionthat the fuel injection amount is not extremely large or small or acombination thereof.

Further, a constant time is needed until the air passing the air flowmeter is introduced into the combustion chamber.

Further, a constant time is needed until the exhaust gas discharged fromthe combustion chamber reaches the upstream oxygen concentration sensor.

Further, it is preferred that the detected and estimated air-fuel ratiosused for calculating the air-fuel ratio difference ratio by the formula9 are those relating to the mixture gas at the same time.

Thus, in the above-explained embodiment, when the estimated iscalculated, the dead time and the time constant relating to the airuntil it is introduced after passing the air flow meter are consideredwhile the dead time and the time constant relating to the exhaust gasuntil it reaches the upstream oxygen concentration sensor after beingdischarged from the combustion chamber are considered.

Further, in the above-explained embodiment, the learned correction valueupdate may be performed independently of the engine operation conditionor only when the engine operation condition meets a defined operationcondition.

The defined operation condition is, for example, a condition that thedetected air-fuel ratio is not extremely rich or lean or a conditionthat the detected air-fuel ratio change is relatively small or acondition that the fuel injection amount change is relatively small or acondition that the intake pressure change is relatively small or acombination of at least two of these conditions.

Further, in the above-explained embodiment, the learned correction valueupdate may be terminated by replacing the not-updated learned correctionvalue with the updated learned correction value directly or by changingthe not-updated learned correction value toward the updated learnedcorrection value progressively and replacing the not-updated learnedcorrection value with the updated learned correction value finally (i.e.a so-called “leveling processing” may be applied to the learnedcorrection value update.).

Further, the air-fuel ratio difference (i.e. the difference of theestimated air-fuel ratio relative to the air-fuel ratio of the mixturegas calculated on the basis of the detected oxygen concentration) mayoccur due to the cause other than the fuel injection amount difference,the detected fresh air amount difference and detected oxygenconcentration difference.

In this regard, in the base that the air-fuel ratio difference due tothe cause other than the fuel injection amount, detected fresh airamount and detected oxygen concentration differences is extremely large,the learned correction value becomes extremely large and as a result,the base correction value becomes extremely large and finally, thecorrection values for the target fuel injection amount correction andthe detected fresh air amount correction become extremely large.

In this case, the target fuel injection amount correction by thecorrection value for the target fuel injection amount correction and thedetected fresh air amount correction by the correction value for thedetected fresh air amount correction become extremely large.

In this regard, in the above-explained embodiment, in order to avoid theexcess corrections of the target fuel injection amount and the detectedfresh air amount, suitable values may be set as the upper limit of thelearned correction value (this value is positive and hereinafter, willbe referred to as—upper limit learned correction value—) and the lowerlimit of the learned correction value (this value is negative andhereinafter, will be referred to as—lower limit learned correctionvalue), respectively and then, the learned correction value may belimited to the upper learned correction value when the learnedcorrection value corrected by the instant correction value is positiveand larger than the upper limit correction value and on the other hand,the learned correction value may be limited to the lower limitcorrection value when the learned correction value corrected by theinstant correction value is negative and smaller than the lower limitcorrection value (i.e. the learned correction value and the lower limitlearned correction value are negative and therefore, the absolute valueof the learned correction value is larger than that of the lower limitlearned correction value).

Further, in place of the learned correction value limitation using theupper and lower limit learned correction values, suitable values may beset as the upper limit value of the base correction value (this value ispositive and hereinafter, will be referred to as—upper limit basecorrection value—) and the lower limit value of the base correctionvalue (this value is negative and hereinafter, will be referred toas—lower limit base correction value—), respectively and then, the basecorrection value may be limited to the upper limit base correction valuewhen the base correction value calculated by the formula 10 is positiveand larger than the upper limit base correction value and on the otherhand, the base correction value may be limited to the lower limit basecorrection value when the base correction value calculated by theformula 10 is negative and smaller than the lower limit base correctionvalue (i.e. the base correction value and the lower limit basecorrection value are negative and therefore, the absolute value of thebase correction value is larger than that of the lower limit basecorrection value).

Further, in place of the learned correction value limitation using theupper and lower limit learned correction value, suitable values may beset as the upper limit value of the correction value for the target fuelinjection amount correction (this value is positive and hereinafter,will be referred to as—upper limit correction value—) and the lowerlimit value of the correction value for the target fuel injection amountcorrection (this value is negative and hereinafter, will be referred toas—lower limit correction value—) and then, the correction valuecalculated by the formula 6 may be limited to the upper limit correctionvalue when the correction value is positive and larger than the upperlimit correction value and on the other hand, the correction valuecalculated by the formula 6 may be limited to the lower limit correctionvalue when the correction value is negative and smaller than the lowerlimit correction value (i.e. the correction value and the lower limitcorrection value are negative and therefore, the absolute value of thecorrection value is larger than that of the lower limit correctionvalue).

Further, in place of the learned correction value limitation using theupper and lower limit learned correction values, suitable values may beset as the upper limit value of the correction value for the detectedfresh air amount correction (this value is positive and hereinafter,will be referred to as—upper limit correction value) and the lower limitvalue of the correction value for the detected fresh air amountcorrection (this value is negative and hereinafter, will be referred toas—lower limit correction value), respectively and then, the correctionvalue calculated by the formula 7 may be limited to the upper limitcorrection value when the correction value is positive and larger thanthe upper limit correction value and on the other hand, the correctionvalue calculated by the formula 7 may be limited to the lower limitcorrection value when the correction value is negative and smaller thanthe lower limit correction value (i.e. the correction value and thelower limit correction value are negative and therefore, the absolutevalue of the correction value is larger than that of the lower limitcorrection value).

Further, the first embodiment relating to the setting is one that theinvention is applied to the case that the absolute values of thepositive and negative fuel injector tolerances are the same as eachother (i.e. X).

However, the invention can be applied to the case that the absolutevalues of the positive and negative fuel injector tolerances aredifferent from each other.

In this case, it is preferred that when producing the fuel injectionamount difference of the fuel injector tolerance having the largerabsolute value, the NOx production amount during the engine operationwith the distribution coefficient being “0” is used as “NOXi0” of theformula 11 while the NOx production amount during the engine operationwith the distribution coefficient being “1” is used as “NOXi1” of theformula 12.

Further, the first embodiment relating to the setting is one that theinvention is applied to the case that the absolute values of thepositive and negative air flow meter tolerances are the same as eachother (i.e. Y).

However, the invention can be applied to the case that the absolutevalues of the positive and negative air flow meter tolerances aredifferent from each other.

In this case, it is preferred that hen producing the detected fresh airamount difference having the larger absolute value, the NOx productionamount during the engine operation with the distribution coefficientbeing “0” is used as “NOXa0” of the formula 13 while the NOx productionamount during the engine operation with the distribution coefficientbeing “1” is used as “NOXal” of the formula 14.

Further, the first embodiment relating to the setting is one that theinvention is applied to the case the absolute values of the positive andnegative oxygen concentration sensor tolerances are the same as eachother (i.e. Z).

However, the invention can be applied to the case that the absolutevalues of the positive and negative oxygen concentration sensortolerances are different from each other.

In this case, it is preferred that when producing the detected oxygenconcentration differece of the oxygen concentration sensor tolerancehaving the larger absolute value, the NOx production amount during theengine operation with the distribution coefficient being “0” is used as“NOXo0” of the formula 15 while the NOx production amount during theengine operation with the distribution coefficient being “1” is used as“NOXo1” of the formula 16.

Further, in the first embodiment relating to the setting, when the totalsum running distance is shorter than the base total sum runningdistance, the distribution coefficient acquired from the firstdistribution coefficient map is set as the distribution coefficient forthe engine control and on the other hand, when the total sum runningdistance is equal to or longer than the base total sum running distance,the distribution coefficient acquired from the second distributioncoefficient map is set as the distribution coefficient for the enginecontrol.

However, in place of this, the distribution coefficient depending on thetotal sum running distance may be calculated by the interpolationdepending on the total sum running distance between the distributioncoefficients acquired respectively from the first and seconddistribution coefficient maps on the basis of the current fuel injectionamount and the current engine speed, and this calculated distributioncoefficient may be set as the distribution coefficient for the enginecontrol.

Further, in the first embodiment relating to the setting, the twodistribution coefficient maps are prepared, one of which is the firstmap used when the total sum running distance is shorter than the basetotal sum running distance and the other of which is the second map usedwhen the total sum running distance is equal to or longer than the basedistance.

However, two or more distribution coefficient maps may be prepareddepending on the total sum running distance, one of them may be selecteddepending on the total distance and the distribution coefficientacquired from the selected map may be set as that for engine control.

In the case that two or more distribution coefficient maps are prepareddepending on the total sum running distance, all maps can be prepared bythe process relating to the setting explained relating to the firstembodiment.

However, there are proportional relationships between the fuel injectionamount difference and NOx index value, between the detected fresh airamount differece and the NOx index value and between the detected oxygenconcentration difference and the NOx index value.

That is, the NOx index value increases in proportion to the increase ofthe fuel injection amount difference, in proportion to the increase ofthe detected fresh air amount difference and in proportion to theincrease of the detected oxygen concentration difference.

Therefore, without acquiring the data of the NOx index value used forpreparing all distribution coefficient maps by the above-explainedprocess, only the data of the NOx index value used for preparing atleast two distribution coefficient maps by the above-explained maps maybe acquired, the NOx index value for preparing the remaining maps may beacquired by the calculation in consideration of the proportionalrelationship between the fuel injection amount difference and the NOxindex value or the proportional relationship between the detected freshair amount difference and the NOx index value or the proportionalrelationship between the detected oxygen concentration difference andthe NOx index value on the basis of the acquired data, and each map maybe prepared.

In the first embodiment relating to the setting, in place of the totalsum running distance, a total sum engine operation time (i.e. the totalsum operation time of the engine) may be used.

In this case, when the total sum engine operation time is shorter than abase total sum engine operation time (i.e. a base total sum engineoperation time corresponding to the base total sum running distance),the distribution coefficient acquired from the first distributioncoefficient map is set as the distribution coefficient for the enginecontrol and on the other hand, when the total time is equal to or longerthan the base time, the distribution coefficient acquired from thesecond distribution coefficient map is set as the distributioncoefficient for the engine control.

The total sum running distance and the total sum engine operation timerepresent the deterioration degrees of the injector, the air flow meterand the upstream oxygen concentration sensor and these degrees decreasesas the total distance or the total time decreases and these degreesincreases as the total distance or the total time increases.

Therefore, it can be understood that the first embodiment of the settingsets the distribution coefficient acquired from the first distributioncoefficient map as the distribution coefficient for the engine controlwhen the deterioration degrees of the injector, the air flow meter andthe upstream oxygen concentration sensor are smaller than apredetermined base deterioration degree (i.e. a deterioration degreecorresponding to the base total sum running distance or the base totalsum engine operation time) and on the other hand, sets the distributioncoefficient acquired from the second distribution coefficient map as thedistribution coefficient for the engine control when the deteriorationdegrees of the injector, the air flow meter and the upstream sensor areequal to or larger than the base deterioration degree.

In the second embodiment relating to the setting, the detection of theNOx production amount is, for example, performed on the basis of anoutput value from a sensor for detecting a NOx concentration in theexhaust gas (hereinafter, this sensor will be referred to as—NOxconcentration sensor—) arranged in the exhaust passage.

The oxygen concentration in the exhaust gas may be detected by using amechanism of the NOx concentration sensor for detecting the NOxconcentration.

Therefore, in this case, in the second embodiment relating to thesetting, in place of the detection of the oxygen concentration (i.e. theair-fuel ratio of the mixture gas) in the exhaust gas by the upstreamoxygen concentration sensor, the oxygen concentration (i.e. the air-fuelratio of the mixture gas) in the exhaust gas by the NOx sensor may bedetected.

In the second embodiment relating to the setting, the predeterminedvalue, a value smaller than the base distribution coefficient by whichpredetermined value when detecting the NOx production amount NOXds ofthe formula 18 may be the same as or different from the predeterminedvalue,

In the second embodiment relating to the setting, the predeterminedvalue, by which a value smaller than the base distribution coefficientis set to a new base distribution coefficient when it is judged that theindex value IDs calculated by the formula 18 is the smallest one may bethe same or different from the predetermined value, by which a valuelarger than the base distribution coefficient is set to a new basedistribution coefficient when it is judged that the index value IDicalculated by the formula 19 is the smallest one.

In the second embodiment relating to the setting, the predeterminedvalue, by which a value smaller than the base distribution coefficientis set to the provisional distribution coefficient when the NOxproduction amount NOXds of the formula 18 is detected may be the same ordifferent from the predetermined value, by which a value smaller thanthe base distribution coefficient is set to the new base distributioncoefficient when it is judged that the index value IDs calculated by theformula 18 is the smallest one (or the predetermined value, by which avalue larger than the base distribution coefficient is set to a new basedistribution coefficient when it is judged that the index value ID1calculated by the formula 19 is the smallest one).

In the second embodiment relating to the setting, the predeterminedvalue, by which a value larger than the distribution coefficient is setto a provisional distribution coefficient when the NOx production amountNOXd1 of the formula 19 is detected may be the same or different fromthe predetermined value, by which a value smaller than the basedistribution coefficient is set a new base distribution coefficient whenit is judged that the index value IDs calculated by the formula 18 isthe smallest one (or the predetermined value, by which a value largerthan the base distribution coefficient is set to a new base distributioncoefficient when it is judged that the index value ID1 calculated by theformula 19 is the smallest one).

In the second embodiment relating to the distribution setting, thesetting of the distribution coefficient may be performed independentlyof the engine operation condition and the setting of the distributioncoefficient may be performed only when the engine operation condition isone suitable for the detection of the NOx concentration by the NOxconcentration sensor (i.e. when the engine operation condition is onewhere the NOx concentration is detected by the accuracy larger than thepredetermined accuracy by the NOx concentration sensor).

In the case that the distribution coefficient is set by the setting ofthe second embodiment, as the initial value of the distributioncoefficient after the injector of the engine is replaced with a new oneor the air flow meter of the engine is replaced with a new one or theupstream oxygen concentration sensor of the engine is replaced with anew one, the distribution coefficient used before the replacement of theinjector or the air flow meter or the upstream oxygen sensor or “1” maybe employed.

The large distribution coefficient is preferred in order to avoid theexcessive correction of the target fuel injection amount or the detectedfresh air amount by the correction value for the excessive large targetfuel injection amount or detected fresh air amount correction which isled when the detected oxygen concentration difference is considerablylarge and therefore, the employment of “1” as the initial value of thedistribution coefficient is preferred in order to avoid such anexcessive correction.

In the case that the distribution coefficient is set by the setting ofthe second embodiment, any value (which is equal to or larger than “0”and equal to or smaller than “1”) may be employed as the initial valueof the distribution coefficient after the reset of the presently-useddistribution coefficient.

However, the large distribution coefficient is preferred in order toavoid the excessive correction of the target fuel injection amount ordetected fresh air amount by the excessive large correction value forthe target fuel injection amount correction or the detected fresh airamount correction which is led when the detected oxygen concentrationdifference is considerably large and therefore, the employment of “1” asthe initial value of the distribution coefficient is preferred in orderto avoid such an excessive correction.

In the second embodiment relating to the setting, a predetermined numberof the base index values may be calculated by the formula 17, theaverage value of these calculated values may be calculated and thiscalculated average value may be compared with the decrease-side andincrease side NOx index values.

Similarly, a predetermined number of the decrease-side NOx index valuesmay be calculated by the formula 18, the average value of thesecalculated values may be calculated and this calculated average valuemay be compared with the base and increase-side NOx index values.

Similarly, a predetermined number of the increase-side NOx index valuesmay be calculated by the formula 19, the average value of thesecalculated values may be calculated and this calculated average valuemay be compared with the base and decrease-side NOx index values.

In the case that the setting of the second embodiment is employed, ifthe correction of the target fuel injection amount by the correctionvalue for target fuel injection amount correction or of the detectedfresh air amount by the correction value for the detected fresh airamount correction may not be performed, it is preferred that the settingof the distribution coefficient is performed on condition of performingthis correction.

In the case that the setting of the second embodiment is employed, thedistribution coefficient setting may be performed independently of theengine condition or only when a specific engine condition is satisfied.

The specific engine condition is, for example, one where a predeterminedtime has elapsed or the vehicle has run for a predetermined runningdistance.

That is, the setting may be performed every the predetermined time haselapsed or the vehicle has run for the predetermined running distance.

As the initial base distribution coefficient of the setting of thesecond embodiment, a value other than the presently-used distributioncoefficient may be set.

However, in consideration of the fact that the presently-useddistribution coefficient becomes a value for maintaining the NOxproduction amount at a desired amount or a near value, it is preferredthat the presently-used distribution coefficient is set as the initialcoefficient of the setting of the second embodiment in order to maintainthe NOx production amount at the desired amount.

In the above-explained embodiments, it is a given fact that thedistribution coefficient is equal to or smaller than “1”.

Therefore, in the case that “1” is set as the initial base distributioncoefficient of the setting of the second embodiment, a value larger thanthe base coefficient by the predetermined value cannot be set andtherefore, the increase-side NOx index value cannot be calculated by theformula 19.

In this case, the base NOx index value calculated by the formula 17 iscompared with the decrease-side NOx index value calculated by theformula 18 and then, if the base NOx index value is smaller than orequal to the decrease-side NOx index value, the setting is terminated bysetting the base coefficient (i.e. “1”) to the distribution coefficient,and on the other hand, if the decrease-side NOx index value is smallerthan the base NOx index value, a value smaller than the base coefficientby the predetermined value is set as a new base coefficient andthereafter, the process explained relating to the setting of the secondembodiment is repeated.

When the base NOx index value is equal to the decrease-side NOx indexvalue, the setting of the distribution coefficient may be terminated bysetting a value smaller than the base coefficient by the predeterminedvalue as the distribution coefficient.

However, the large distribution coefficient is preferred in order toavoid the excessive correction of the target fuel injection amount ordetected fresh air amount by the excessive correction value for thetarget fuel injection amount correction or detected fresh air amountcorrection which is led in the case that the detected oxygenconcentration difference is considerably large and therefore, it ispreferred that the base coefficient (i.e. “1”) is set as thedistribution coefficient when the base NOx index value is equal to thedecrease-side NOx index value in order to avoid such an excessivecorrection.

The base coefficient may become “1” during the setting of the secondembodiment.

In this case, a value larger than the base coefficient by thepredetermined value cannot be set and therefore, the increase-side NOxindex value cannot be calculated by the formula 19.

In this case, the base NOx index value calculated by the formula 17 iscompared with the decrease-side NOx index value calculated by theformula 18 and then, if the base value is smaller than or equal to thedecrease-side NOx index value, the setting of the distributioncoefficient is terminated by setting the base coefficient (i.e. “1”) asthe distribution coefficient and on the other hand, if the decrease-sideNOx index value is smaller than the base NOx index value, a valuesmaller than the base coefficient by the predetermined value is set as anew base coefficient and thereafter, the process explained relating tothe setting of the second embodiment is repeated.

In the above-explained embodiments, it is given fact that thedistribution coefficient is equal to or larger than “0”.

Therefore, in the case that “0” is set as the initial base coefficientof the setting of the second embodiment, a value smaller than the basecoefficient by the predetermined value cannot be set and therefore, thedecrease-side NOx index value cannot be calculated by the formula 18.

In this case, the base NOx index value calculated by the formula 17 iscompared with the increase-side NOx index value calculated by theformula 19 and then, if the base value is smaller than the increase-sidevalue, the setting of the distribution coefficient is terminated bysetting the base coefficient (i.e. “0”) as the distribution coefficient,if the base value is equal to the increase-side value, the setting ofthe distribution coefficient is terminated by setting a value largerthan the base coefficient as the distribution coefficient and if theincrease-side value is smaller than the base value, a value larger thanthe base coefficient by the predetermined value is set as a new basecoefficient and thereafter, the process explained relating to thesetting of the second embodiment is repeated.

When the base value is equal to the increase-side value, the setting ofthe distribution coefficient may be terminated by setting the basecoefficient as the distribution coefficient.

However, the large distribution coefficient is preferred in order toavoid the excessive correction of the target fuel injection amount ordetected fresh air amount by the excessive large correction value forthe target fuel injection amount correction or detected fresh air amountcorrection which is led in the case that the detected oxygenconcentration difference is considerably large and therefore, it ispreferred that a value larger than the base coefficient by thepredetermined value is set as the distribution coefficient when the baseNOx index value is equal to the increase-side value in order to avoidsuch an excessive correction.

The base coefficient may become “0” during the setting of the secondembodiment.

In this case, a value smaller than the base coefficient by thepredetermined value cannot be set and therefore, the decrease-side NOxindex value cannot be calculated by the formula 18.

In this case, the base value calculated by the formula 17 is comparedwith the increase-side value calculated by the formula 19 and if thebase value is smaller than the increase-side value, the setting of thedistribution coefficient is terminated by setting the base coefficient(i.e. “0”) as the distribution coefficient, if the base value is equalto the increase-side value, the setting is terminated by setting a valuelarger than the base coefficient by the predetermined value as thedistribution coefficient and if the increase-side value is smaller thanthe base value, a value larger than the base coefficient by thepredetermined value is set as a new distribution coefficient andthereafter, the process explained relating to the setting of the secondembodiment is repeated.

In the case that the setting of the distribution coefficient of thesecond embodiment is employed, the malfunction diagnosis of the injectoror air flow meter may be performed during the engine operationindependently of whether the setting of the distribution coefficient iscompleted or the malfunction diagnosis of the injector or air flow metermay not be performed during the setting of the distribution coefficientand then, the diagnosis may be performed when the setting of thedistribution coefficient is completed.

In the case that the limitation of the learned correction value by theupper and lower learned correction values or the limitation of the basecorrection value by the upper and lower base correction values or thelimitation of the correction value for the target fuel injection amountcorrection by the upper and lower correction value is performed, it ispreferred that the correction value for the target fuel injection amountcorrection calculated using the unlimited learned or base correctionvalue or the unlimited correction value for the target fuel injectionamount correction is employed as the correction value for the targetfuel injection amount correction used for the injector malfunctiondiagnosis.

In the case that the limitation of the learned correction value by theupper and lower learned correction values or the limitation of the basecorrection value by the upper and lower base correction values or thelimitation of the correction value for the detected fresh air amountcorrection by the upper and lower correction value is performed, it ispreferred that the correction value for detected fresh air amountcorrection calculated using the unlimited learned or base correctionvalue or the unlimited correction value for the detected fresh airamount correction is employed as the correction value for the detectedfresh air amount correction used for the air flow meter malfunctiondiagnosis.

The above-explained embodiments are those that the invention is appliedto the case that the EGR control valve opening is controlled to controlthe EGR rate.

However, the invention can be applied to the control of the throttlevalve opening as well as the EGR control valve opening degree to controlthe EGR rate.

In addition, the invention can be applied to the control of the throttlevalve opening degree without the EGR control valve opening degree tocontrol the EGR rate.

The engine of the above-explained embodiments comprises a superchargerhaving an exhaust turbine arranged in the exhaust passage and acompressor arranged in the intake passage and the turbine of thesupercharger has vanes for controlling the air compression by thecompressor, the invention can be applied to the control of a vaneopening degree as well as the EGR control valve opening degree tocontrol the EGR rate.

In addition, the invention can be applied to the control of the vaneopening degree without the EGR control valve opening degree to controlthe EGR rate.

The above-explained embodiments is those that the invention is appliedto the case that the fuel injection amount used for the target EGR ratesetting is corrected by the correction value introduced from the basecorrection value (i.e. the correction value for the target fuelinjection amount correction).

However, the invention can be applied to the correction of the enginespeed as well as the fuel injection amount used for the target EGR ratesetting by the correction value introduced from the base correctionvalue.

The invention can be applied to the correction of the engine speedwithout the fuel injection amount used for the target EGR rate settingby the correction value introduced from the base correction value.

The above-explained embodiments are those that the invention is appliedto the case that the engine speed and the fuel injection amount are usedfor the target EGR rate setting.

However, the invention can be applied to the case that the engine speed,the fuel injection amount and parameter(s) other than them are used forthe target EGR rate setting.

In this case, in addition to or in place of the correction of the fuelinjection amount used for the target EGR rate setting by the correctionvalue introduced from the base correction value (i.e. the correctionvalue for the target fuel injection amount correction), the addedparameter(s) may be corrected by the correction value introduced fromthe base correction value.

The invention can be applied to the case that the engine speed and thefuel injection amount are not used and parameter(s) other than themis/are used for the target EGR rate setting.

In this case, the added parameter(s) is/are corrected by the correctionvalue introduced from the base correction value.

The above-explained embodiments are those that the invention is appliedto the correction of the fuel injection amount for the target EGR rateacquisition, the detected fresh air amount for the estimated EGR ratecalculation, the detected fresh air amount for the estimated air-fuelratio calculation and the estimated fuel injection amount for theestimated air-fuel ratio calculation.

However, the invention can be applied to the correction of parameterssuch as a fuel injection command given to the injector, a command givento the throttle valve, etc. other than the above-mentioned parameters.

In the above-explained embodiments, the fuel injection amount for thetarget EGR rate acquisition is corrected, however, the actual EGR ratechanges by changing the target EGR rate and thereby, the fresh airamount changes.

Therefore, the EGR control valve of the above-explained embodiments ismeans for controlling the amount of the air supplied to the combustionchamber and the correction of the fuel injection amount for the targetEGR rate acquisition of the above-explained embodiment is a correctionof the amount of the air supplied to the combustion chamber.

The above-explained embodiments are those that the invention is appliedto the compression self-ignition engine.

However, the invention can be applied to a spark ignition internalcombustion engine (so-called gasoline engine).

1. A control device of an internal combustion engine, comprising: meansfor supplying a fuel to a combustion chamber; means for giving to thefuel supply means, a command for supplying the fuel of a target amountto the combustion chamber by the fuel supply means; means for estimatingan amount of the fuel supplied to the combustion chamber from the fuelsupply means on the basis of the fuel supply command; means forcontrolling an amount of an air supplied to the combustion chamber;means for giving to the air supply amount control means, a command forsupplying the air of a target amount to the combustion chamber by theair supply amount control means; means for detecting an amount of theair supplied to the combustion chamber; means for estimating an air-fuelratio of a mixture gas formed in the combustion chamber on the basis ofthe amount of the fuel estimated by the fuel supply amount estimationmeans and the amount of the air detected by the air amount detectionmeans; means for detecting the air-fuel ratio; and means for performingan air-fuel ratio control for making the air-fuel ratio estimated by theair-fuel ratio estimation means and the air-fuel ratio detected by theair-fuel ratio detection means correspond to each other, using theestimated fuel supply amount and the detected air amount or the airsupply command, wherein the device calculates on a difference of theestimated air-fuel ratio relative to the detected air-fuel ratio, acorrection value for correcting the fuel supply amount estimated by thefuel supply amount estimation means to make the estimated and detectedair-fuel ratios correspond to each other when these ratios do notcorrespond to each other, acquires as a fuel supply differenceproportion, a rate of he air-fuel ratio difference due to the fuelsupply difference of the fuel supply means occupying the air-fuel ratiodifference and acquiring, as an air amount detection differenceproportion, a rate of the air-fuel ratio difference due to the airamount detection difference of the air amount detection means occupyingthe air-fuel ratio difference, calculates a correction value forcorrecting the estimated fuel supply amount and a correction value forcorrecting the detected air amount or the air supply command by dividingthe correction value for the estimated fuel supply amount correctionusing these rates, performs the air-fuel ratio control using theestimated fuel supply amount corrected by the correction value for thefuel supply difference compensation and the detected air amount or theair supply command corrected by the correction value for the air amountdetection difference compensation, and wherein the device divides thecorrection value for the estimated fuel supply amount correction to thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation such that a valueequivalent to the air-fuel ratio difference calculated using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation, becomes equal to theair-fuel ratio difference.
 2. The device of claim 1, wherein theair-fuel ratio difference is a difference equivalent value calculated bysubtracting 1 from a ratio of the estimated air-fuel ratio relative tothe detected air-fuel ratio and the device calculates the correctionvalue for the estimated fuel supply amount correction as a value formaking the difference equivalent value zero.
 3. The device of claim 1,wherein the device acquires as a first particular component amount, anamount of a particular component of the exhaust gas discharged from thecombustion chamber when the air-fuel ratio control is performed usingthe estimated fuel supply amount corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has an error and the air amount detection means has noerror, wherein the device acquires as a second particular componentamount, an amount of the particular component when the air-fuel ratiocontrol is performed using the estimated fuel supply amount notcorrected by the correction value for the fuel supply differencecompensation and the detected air amount or the air supply commandcorrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas an error and the air amount detection means has no error, whereinthe device acquires as a third particular component amount, an amount ofthe particular component when the air-fuel ratio control is performedusing the estimated fuel supply amount corrected by the correction valuefor the fuel supply difference compensation and the detected air amountor the air supply command not corrected by the correction value for theair amount detection difference compensation under the condition wherethe fuel supply means has no error and the air amount detection meanshas an error, wherein the device acquires as a fourth particularcomponent amount, an amount of the particular component when theair-fuel ratio control is performed using the estimated fuel supplyamount not corrected by the correction value for the fuel supplydifference compensation and the detected air amount or the air supplycommand corrected by the correction value for the air amount detectiondifference compensation under the condition where the fuel supply meanshas no error and the air amount detection means has an error, andwherein the device obtains the fuel supply difference and air amountdetection difference proportions on the basis of the four acquiredparticular component amounts.
 4. The device of claim 1, wherein thedevice acquires as a first particular component amount, an amount of aparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means has an error and the air amount detection means andthe air-fuel ratio detection means have no error, wherein the deviceacquires as a second particular component amount, an amount of theparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount not corrected by the correction valuefor the fuel supply difference compensation and the detected air amountor the air supply command corrected by the correction value for the airamount detection difference compensation under the condition where fuelsupply means has an error and the air amount detection means and theair-fuel ratio detection means have no error, wherein the deviceacquires as a third particular component amount, an amount of theparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air-fuel ratio detection means have no errorand the air amount detection means has an error, wherein the deviceacquires as a fourth particular component amount, an amount of theparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount not corrected by the correction valuefor the fuel supply difference compensation and the detected air amountor the air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air-fuel ratio detection means have no errorand the air amount detection means has an error, wherein the deviceacquires as a fifth particular component amount, an amount of theparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount corrected by the correction value forthe fuel supply difference compensation and the detected air amount orthe air supply command not corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air amount detection means have no error andthe air-fuel ratio detection means has an error, wherein the deviceacquires as a sixth particular component amount, an amount of theparticular component when the air-fuel ratio control is performed usingthe estimated fuel supply amount not corrected by the correction valuefor the fuel supply difference compensation and the detected air amountor the air supply command corrected by the correction value for the airamount detection difference compensation under the condition where thefuel supply means and the air amount detection means have no error andthe air-fuel ratio detection means has an error, and wherein the deviceobtains the fuel supply difference and air amount detection differenceproportions on the basis of the six acquired particular componentamounts.
 5. A control device of an internal combustion engine,comprising: means for supplying a fuel to a combustion chamber; meansfor giving to the fuel supply means, a command for supplying the fuel ofa target amount to the combustion chamber by the fuel supply means;means for estimating an amount of the fuel supplied to the combustionchamber from the fuel supply means on the basis of the fuel supplycommand; means for controlling an amount of an air supplied to thecombustion chamber; means for giving to the air supply amount controlmeans, a command for supplying the air amount of a target amount to thecombustion chamber by the air supply amount control means; means fordetecting the amount of the air supplied to the combustion chamber;means for estimating an air-fuel ratio of a mixture gas formed in thecombustion chamber on the basis of the fuel amount estimated by the fuelsupply amount estimation means and the air amount detected by the airamount detection means; means for detecting the air-fuel ratio, andmeans for performing an air-fuel ratio control for making the air-fuelratios estimated by the air-fuel ratio estimation means and detected bythe air-fuel ratio detection means correspond to each other, using thefuel supply command and the detected air amount or the air supplycommand, wherein the device calculates on the basis of a difference ofthe estimated air-fuel ratio relative to the detected air-fuel ratio, acorrection value for the fuel supply command correction for making theestimated and detected air-fuel ratios by correcting the command givento the fuel supply means when the estimated and detected air fuel ratiosdo not correspond to each other, acquires as a fuel supply differenceproportion, a rate of the air-fuel ratio difference due to the fuelsupply difference of the fuel supply means occupying the air-fuel ratiodifference and acquiring, as an amount detection difference proportion,a rate of the air-fuel ratio difference due to the air amount detectiondifference of the air amount detection means occupying the air-fuelratio difference, calculates a correction value for correcting the fuelsupply command and a correction value for correcting the detected airamount or the air supply command by dividing the correction value forthe fuel supply command correction, using these rates, and performs theair-fuel ratio control using the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount or the air supply command corrected by thecorrection value for the air amount detection difference compensation,and wherein the device divides the correction value for the fuel supplycommand correction to the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation such that an air-fuel ratio difference equivalent value,equivalent to the air-fuel ratio difference, calculated using thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation.
 6. The device of claim 5,wherein the air-fuel ratio difference is a difference equivalent valuecalculated by subtracting 1 from a ratio of the estimated air-fuel ratiorelative to the detected air-fuel ratio and the correction value for thefuel supply command correction is calculated as a value for making thedifference equivalent value zero. 7-12. (canceled)
 13. A control deviceof an internal combustion engine, comprising: means for supplying a fuelto a combustion chamber; means for giving to the fuel supply means, acommand for supplying the fuel of a target amount to the combustionchamber by the fuel supply means; means for estimating an amount of thefuel supplied to the combustion chamber from the fuel supply means onthe basis of the fuel supply command; means for controlling an amount ofan air supplied to the combustion chamber; means for giving to the airsupply amount control means, a command for supplying the air of a targetamount to the combustion chamber by the air supply amount control means;means for detecting the amount of the air supplied to the combustionchamber; means for estimating an air-fuel ratio of a mixture gas formedin the combustion chamber on the basis of the fuel amount estimated bythe fuel supply amount estimation means and the air amount detected bythe air amount detection means; means for detecting the air-fuel ratio;and means for performing an air-fuel ratio control for making theair-fuel ratios estimated by the air-fuel ratio estimation means anddetected by the air-fuel ratio detection means correspond to each other,using the estimated fuel supply amount or the fuel supply command andthe detected air amount, wherein the device calculates on the basis of adifference of the estimated air-fuel ratio relative to the detectedair-fuel ratio, a correction value for the detected air amountcorrection for correcting the air amount detected by the air amountdetected means to make the estimated and detected air-fuel ratioscorrespond to each other when the estimated and detected air-fuel ratiosdo not correspond to each other, acquires as a fuel supply differenceproportion, a rate of the air-fuel ratio difference due to the fuelsupply difference of the fuel supply means occupying the air-fuel ratiodifference and acquiring, as an air amount detection differenceproportion, a rate of the air-fuel ratio difference due to the airamount detection difference of the air amount detection means occupyingthe air-fuel ratio difference, calculates a correction value for a fuelsupply difference compensation for correcting the estimated fuel supplyamount or fuel supply command and a correction value for an air amountdetection difference compensation for correcting the detected amount bydividing the correction value for the detected air amount correction,using these rates, and performs the air-fuel ratio control, using theestimated fuel supply amount or the fuel supply command corrected by thecorrection value for the fuel supply difference compensation and thedetected air amount corrected by the correction value for the air amountdetection difference compensation, and wherein the device divides thecorrection value for the detected air amount correction to thecorrection values for the fuel supply difference compensation and theair amount detection difference compensation such that the air-fuelratio difference equivalent value equivalent to the air-fuel ratiodifference, calculated using the correction values for the fuel supplydifference compensation and the air amount detection differencecompensation, becomes equal to the air-fuel ratio difference.
 14. Thedevice of claim 13, wherein the air-fuel ratio difference is adifference equivalent value calculated by subtracting 1 from a ratio ofthe estimated air-fuel ratio relative to the detected air-fuel ratio andthe correction value for the detected air amount correction iscalculated as a value for making the difference equivalent value zero.15-24. (canceled)
 25. The device of claim 1, wherein the engine furthercomprises exhaust gas recirculation means for introducing to an intakepassage the exhaust gas discharged to an exhaust passage from thecombustion chamber, the device determines a target recirculated exhaustgas amount of the exhaust gas introduced to the intake passage by theexhaust gas recirculation means on the basis of the estimated fuelsupply amount and the device uses the estimated fuel supply amountcorrected by the correction value for the fuel supply differencecompensation for the determination of the target recirculated exhaustgas amount.
 26. The device of claim 25, wherein the engine furthercomprises actual recirculated exhaust gas amount estimation means forestimating an amount of the exhaust gas actually introduced to theintake passage by the exhaust gas recirculation means, using thedetected air amount and wherein the device uses the detected air amountcorrected by the correction value for the air amount detectiondifference compensation for the estimation of the amount by the actualrecirculated exhaust gas amount estimation means.
 27. The device ofclaim 26, wherein the device controls the amount of the exhaust gasintroduced to the intake passage by the exhaust gas recirculation meanssuch that the amount estimated by the actual recirculated exhaust gasamount estimation means corresponds to the target recirculated exhaustgas amount.
 28. The device of claim 1, wherein the engine furthercomprises means for detecting an amount of a particular component of theexhaust gas discharged from the combustion chamber, wherein the devicesets a base of the fuel supply difference proportion as a base fuelsupply difference proportion and sets the air amount detectiondifference proportion corresponding to this base rate as a base airamount detection difference proportion, acquires as a base particularcomponent amount, by the particular component amount detection means,the amount of the particular component of the exhaust gas dischargedfrom the combustion chamber when the air-fuel ratio control is performedusing these rate, sets a rate larger than the base fuel supplydifference proportion as a first comparison fuel supply differenceproportion and sets the air amount detection difference proportioncorresponding to this first rate as a first comparison air amountdetection difference proportion, acquires as a first comparisonparticular component amount, by the particular component amountdetection means, an amount of the particular component of the exhaustgas discharged from the combustion chamber when the air-fuel ratiocontrol is performed using these first rates, sets a rate smaller thanthe base fuel supply difference proportion as a second comparison fuelsupply difference proportion and sets the air-fuel ratio detectiondifference proportion corresponding to this second rate as a secondcomparison air amount detection difference proportion, acquires as asecond comparison particular component amount, by the particularcomponent amount detection means, an amount of the particular componentof the exhaust gas discharged from the combustion chamber when theair-fuel ratio control is performed using these second rates, whereinthe device employs the base fuel supply difference and base air amountdetection difference proportions as the fuel supply difference and airamount detection difference proportions, respectively when the baseparticular component amount is the smallest among the acquiredparticular component amounts, wherein when the first comparisonparticular component amount is the smallest among the acquiredparticular component amount, the device performs a first process of:setting the first comparison fuel supply and air amount detectiondifference proportions as new base fuel supply and air amount detectiondifference proportions, respectively, acquiring, as the base particularcomponent amount, by the particular component amount detection means,the amount of the particular component of the exhaust gas dischargedfrom the combustion chamber when the air-fuel ratio control is performedusing these new base rates, setting a rate larger than the new base fuelsupply difference proportion as a new first comparison fuel supplydifference proportion and setting the air amount detection differenceproportion corresponding to this first comparison fuel supply differenceproportion as a new first comparison air amount detection differenceproportion, acquiring, as a first comparison particular componentamount, by the particular component amount detection means, the amountof the particular component of the exhaust gas discharged from thecombustion chamber when the air amount control is performed using thesenew first rates, setting a rate smaller than the new base fuel supplydifference proportion as a new second comparison fuel supply differenceproportion and setting the air amount detection difference proportioncorresponding to this second rate as a new second comparison air amountdetection difference proportion, and acquiring as a second comparisonparticular component amount, by the particular component amountdetection means, the amount of the particular component of the exhaustgas discharged from the combustion chamber when the air amount controlis performed using these new second rates, wherein when the secondcomparison particular component amount is the smallest among theacquired particular component amount, the device performs a secondprocess of: setting the second comparison fuel supply and air amountdetection difference proportions as new base fuel supply and air amountdetection difference proportions, respectively, acquiring, as the baseparticular component amount, by the particular component amountdetection means, the amount of the particular component of the exhaustgas discharged from the combustion chamber when the air-fuel ratiocontrol is performed using these new base rates, setting a rate largerthan the new base fuel supply difference proportion as a new firstcomparison fuel supply difference proportion and setting the air amountdetection difference proportion corresponding to this first comparisonfuel supply difference proportion as a new first comparison air amountdetection difference proportion, acquiring, as a first comparisonparticular component amount, by the particular component amountdetection means, the amount of the particular component of the exhaustgas discharged from the combustion chamber when the air amount controlis performed using these new first rates, setting a rate smaller thanthe new base fuel supply difference proportion as a new secondcomparison fuel supply difference proportion and setting the air amountdetection difference proportion corresponding to this second rate as anew second comparison air amount detection difference proportion, andacquiring as a second comparison particular component amount by theparticular component amount detection means, the amount of theparticular component of the exhaust gas discharged from the combustionchamber when the air amount control is performed using these new secondrates, wherein the device performs the first process when the firstcomparison particular component amount is the smallest among theparticular component amounts acquired by the first and second processes,wherein the device performs the second process when the secondcomparison particular component amount is the smallest among theparticular component amounts acquired by the first and second processes,and wherein the device employs as the fuel supply and air amountdetection difference proportions, the base fuel supply and air amountdetection difference proportions, respectively, used in the first andsecond processes when the base particular component amount is thesmallest among the particular component amount acquired by the first andsecond processes.
 29. The device of claim 28, wherein an allowable rangeof the correction value for the fuel supply difference compensation ispreviously set as a fuel supply difference allowable range and thedevice diagnoses that a malfunction occurs in the fuel supply means whenthe correction value for the fuel supply difference compensation is notwithin the fuel supply difference allowable range.
 30. The device ofclaim 28, wherein an allowable range of the correction value for the airamount detection difference compensation is previously set as an airamount detection difference allowable range and the device diagnosesthat a malfunction occurs in the air amount detection means when thecorrection value for the air amount detection difference compensation isnot within the air amount detection difference allowable range.